Costa signed for his first European club in February 2006, Portugal’s Braga. He initially struggled with loneliness and the comparatively cold weather of northern Portugal. Out of action due to the club’s lack of a youth team, he was loaned that summer to Penafiel in the second division, managed by former Portugal international Rui Bento, who desired the “rough diamond”.

Through his negotiations with Spain’s Atlético Madrid, Mendes arranged Costa’s transfer for €1.5 million and 50% of the player’s rights in December 2006, but he remained on loan at Braga until the end of the season. Atlético defeated interest from Porto and Recreativo de Huelva for Costa’s signature, with director Jesús García Pitarch admitting that it was a risk to pay so much for an inexperienced player. After 5 goals in 13 games for Penafiel, he was recalled to Braga in January 2007. On 23 February, he came on in the 71st minute for Zé Carlos and scored his first goal for the team, a last-minute goal for a 1–0 win at Parma to advance 2–0 on aggregate to the Last 16 of the UEFA Cup. His season ended after seven games due to a metatarsal injury which ruled him out for six months.

Costa was presented by Atlético Madrid president Enrique Cerezo on 10 July 2007 as “the new Kaká”. While scout Javier Hernández wished for him to return to fitness in the club’s reserves, García Pitarch instead suggested loaning Costa out immediately. He made his debut on 11 August in the Ciudad de Vigo tournament against Celta de Vigo, replacing Simão at half-time in a penalty shootout victory.

Later that month, Costa and Mario Suárez were loaned to Segunda División side Celta de Vigo for the season, and Costa became a regular in the team, managed by former Ballon d’Or winner Hristo Stoichkov. In his seventh league match, he scored his first goal in Spanish football in a dominant home victory over Xerez; after scoring, he showboated, causing a brawl which resulted in him being sent off. Costa was subsequently rested from Celta’s away game at the same opposition. The event drew the wrath of Stoichkov, who unexpectedly left his position. Towards the middle of the season, he was involved in two further controversies: he struck Málaga defender Weligton in the head, causing an injury which required medical stitches, and was sent off against Sevilla Atlético for diving and dissent, leaving his team to fight for a draw without him. The loyal strike partner of Quincy Owusu-Abeyie despite the pair not sharing a common language, he was dropped for Cypriot Ioannis Okkas. On 23 March 2008, Costa scored both Celta goals in a 2–1 win at Numancia, the latter after a long dribble; but later on in the campaign, he was sent off against Tenerife at Balaídos, after which Celta went from winning 2–0 to drawing 2–2. The team barely avoided relegation, and Costa earned a reputation for being a disruptive influence.

Despite earning a poor reputation for his conduct, Costa attracted interest from Salamanca, Gimnàstic de Tarragona and Málaga after his loan at Celta; García Pitarch ruled out any approach from the latter, fearing how Costa would behave on the Costa del Sol. After attending Atlético’s pre-season tour of Mexico, he signed on loan for Albacete, also of Segunda División, on 22 August 2008, signing a contract which would have a lower fee depending on how many games he played. He initially threatened to terminate his deal with the Castile-La Mancha team, on account of the quality of his teammates and the city’s lack of a beach. Nine days after signing, he scored a late winner in a 2–1 victory over Sevilla’s reserves at the Estadio Carlos Belmonte. The Queso Mecánico suffered with financial problems during Costa’s loan, with him threatening to strike unless their non-playing staff were paid in full. He was dropped to the bench by manager Juan Ignacio Martínez for the home game against Real Sociedad on 13 December as punishment for an argument with goalkeeper Jonathan, but came on as a substitute to score another late winner.

Costa was known for misbehaviour on and off the pitch while at Albacete. He was sent off away to Tenerife, after which he slandered the referee’s mother and confronted his opponents. He pulled practical jokes on his teammates and employers, earning him the moniker “that fucking Brazilian”. However, he was a central figure as they avoided relegation, assisting twice in a 3–0 win at high-flying Rayo Vallecano on 2 May 2009, despite missing a penalty.

On 8 July 2009, Costa was sold to Real Valladolid as part of the deal that sent goalkeeper Sergio Asenjo in the opposite direction, with the transfer including a €1 million buy-back option that could be activated by Atlético at the end of the season. García Pitarch confessed that there was a verbal agreement that Costa would definitely return at the end of the campaign, and that the deal had been made to look permanent in order to give Costa more commitment to his new club.

Initially, Costa had competition up front from fellow new signings Alberto Bueno and Manucho, signed from Real Madrid and Manchester United respectively; he eventually forged a friendship with the latter, a fellow lusophone, from Angola. He started strong for the Castile and León side, scoring 6 times in his first 12 games, but only found the net once in the following five-and-a-half months as the campaign eventually ended in relegation from La Liga. He was sent off in a goalless draw against Espanyol on 24 March 2010 for a stamp on Dídac Vilà in the first half.

In June 2010, Costa returned to the Colchoneros, initially as a backup to Sergio Agüero and Diego Forlán – Atlético also paid an undisclosed sum to Braga to buy all the residual 30% economic rights (the former also had to pay in excess of €833,000 in agent’s fees to Gestifute). He was an unused substitute as Atlético won the 2010 UEFA Super Cup on 27 August.

In July 2011, during Atlético’s pre-season, Costa suffered a serious knee injury, going on to miss the majority of the season. The injury prevented him from passing a medical at Turkish club Beşiktaş, having already agreed to transfer to them. On 23 January 2012, Costa was loaned to fellow league club Rayo Vallecano until June; he scored four goals in his first three appearances, including two in a 5–3 away win against Levante, eventually finishing his loan spell with 10 goals from 16 games.

For the second time in his career, Costa was an unused substitute as Atlético won the UEFA Super Cup on 1 September 2012. That December, Costa was involved in several on-field altercations in two separate matches. The first was in a 0–2 local derby loss against Real Madrid where he avoided disciplinary action after spitting incidents between him and Sergio Ramos. He was sent off in the following game at Viktoria Plzeň in the UEFA Europa League for headbutting opponent David Limberský, and was handed a four-match ban by UEFA. This, however, did not deter coach Diego Simeone from continuing to start him, and he responded by scoring three goals in two home contests, against Deportivo de La Coruña in the league (6–0) and Getafe in the season’s Copa del Rey (3–0).

Costa scored Atlético’s equalising goal in the Copa del Rey final clash against city rivals Real Madrid on 17 May 2013, contributing to the 2–1 triumph – the first in 25 games in a streak stretching back to 1999 – and the tenth win in the tournament, confirmed by Miranda’s extra-time header. He and opponent Cristiano Ronaldo had gone into the match as joint top scorers in the tournament, and thus Costa’s eighth goal made him the top scorer.

In August 2013, Costa was heavily linked with a move to Liverpool, who allegedly matched his release clause of €25 million and offered him three times his salary at Atlético. Costa, however, chose to stay at the club and renewed his contract until 2018, while also doubling his wages; a few days after this, in the first match of the new season on 19 August, he scored a brace in a 3–1 win at Sevilla.

On 24 September, Costa scored both goals in a 2–1 home triumph over Osasuna to help his team stay level on points with league leaders Barcelona through six games. Four days later, in the Madrid derby, he scored the only goal of the game to record a second win over Real at the Santiago Bernabéu in under five months. For his performances, he was crowned the inaugural La Liga Player of the Month for September 2013. By his 25th birthday on 7 October, he had scored ten goals in eight league matches, equalling his tally from the previous season. All of those matches were won by Atlético, setting a new record for the best start to a season. On 23 November 2013, Costa scored an overhead volley from a cross by Gabi in a win over Getafe; the goal was nominated for the FIFA Puskás Award.

On 22 October 2013, Costa marked his UEFA Champions League debut with two goals against Austria Wien, the first coming after a fine individual effort in an eventual 3–0 group stage away win. On 19 February 2014, in the first knockout round’s first leg, he scored the game’s only goal at Milan, scoring seven minutes from time after a corner kick from Gabi; he added a further two in the second match, helping Atlético to a 4–1 victory that put them into the quarter-finals for the first time in 17 years.

On 5 March 2013, Costa was called up to the Brazil national team by head coach Luiz Felipe Scolari for friendlies with Italy in Geneva and Russia in London, both taking place late in that month. He made his debut in the first match on 21 March, replacing Fred midway through the second half of the 2–2 draw. Four days later at Stamford Bridge, he replaced Kaká for the last 12 minutes of a 1–1 draw with Russia.

In September 2013, the Royal Spanish Football Federation made an official request to FIFA for permission to call up Costa for the Spain national team. He had been granted Spanish nationality in July. FIFA regulations currently permit players with more than one nationality to represent a second country if, like Costa, he had only represented his first country in friendly matches.

On 29 October 2013, Costa declared that he wished to play international football for Spain, sending a letter to the Brazilian Football Confederation (CBF). Following the news, Scolari commented, “A Brazilian player who refuses to wear the shirt of the Brazilian national team and compete in a World Cup in your country is automatically withdrawn. He is turning his back on a dream of millions, to represent our national team, the five-time champions in a World Cup in Brazil.”

Earlier in his Atlético Madrid career, Costa’s physical play was used in support of Radamel Falcao, thus ensuring a lower goalscoring rate. After Falcao was sold in 2013, the attack was restructured around Costa by manager Diego Simeone. Simeone, who like Costa was known for his competitiveness and aggression, found ways to enhance his discipline while retaining his determination. In 2014, his club teammate Diego Godín described Costa as the team’s “heartbeat,” commenting that he “gives us everything,” also adding: “Sometimes things aren’t going well and he is able to open up the game with his strength and technique.” Nick Dorrington of Bleacher Report described him as a “battering ram of a striker: Strong, quick and tireless in his pursuit of the ball,” while the club’s manager Simeone lauded his work-rate as being “contagious.”

On 30 April 2014, Costa won and converted a penalty in the second leg of the Champions League semi-final against Chelsea, as Atlético won 3–1 at Stamford Bridge and advanced to the final of the competition for the first time since 1974. He finished the league season with 27 league goals to become the third highest scorer, and the team won the title for the first time since 1996, but he was substituted after 16 minutes of the last match of the season against Barcelona due to a hamstring injury. Atlético sought to cure this injury before the upcoming Champions League final against Real Madrid by sending him to Belgrade for treatment with a horse placenta, and he was included in the starting line-up for the decisive match. However, he left the pitch after eight minutes in an eventual 1–4 loss; manager Diego Simeone later admitted a personal mistake in selecting the player to start the final despite his recent injury. Costa scored eight goals during the Champions League campaign, equalling the record held by Vavá since 1959 for most in a season by an Atlético player, and in his entire career was in the top ten Atlético players by goal average. At the season’s LFP Awards, he was nominated for the league’s Best Forward, losing out to Cristiano Ronaldo.

Having completed his medical in June, Chelsea announced on 1 July 2014 that they had agreed to meet the £32 million buy-out clause in Costa’s contract. On 15 July, Chelsea confirmed the completion of the signing of Costa, who signed a five-year contract on a salary of £150,000 a week. On signing, Costa said, “I am very happy to sign for Chelsea. Everybody knows it is a big club in a very competitive league, and I am very excited to get started in England with a fantastic coach and team-mates. Having played against Chelsea last season I know the high quality of the squad I am joining”. Following the departure of former Chelsea striker Demba Ba, Costa inherited his number 19 shirt, the same number he wore at the 2014 World Cup for Spain and previously at Atlético.

On 28 February 2014, Spain manager Vicente del Bosque included Costa in the squad for a friendly against Italy. He finally made his debut on 5 March, playing the full 90 minutes at his club ground, the Vicente Calderón Stadium, as the hosts won 1–0.

Costa scored his first goal for Spain with the third in a 4–0 UEFA Euro 2016 qualifying win away to Luxembourg on 12 October 2014. He did not feature again for Spain until 5 September 2015, when he was fouled by Slovakia goalkeeper Matúš Kozáčik for a penalty, which Andrés Iniesta converted for a 2–0 qualifying win at the Estadio Carlos Tartiere in Oviedo. He was booed when he was substituted for Paco Alcácer later in the match. Del Bosque defended Costa from criticism, saying that he performed well against the Slovak defence. However, he was not included in the final squad for the tournament.

Ahead of his competitive debut for Chelsea in August 2014, BBC Sport pundit Robbie Savage described Costa as “the missing piece in the jigsaw” for the “clear favourites” who “could end up winning the title by five or six points”. He explained that Chelsea’s defence was already the strongest in the league, but a poorer rate of shot-to-goal conversion had cost them the title. He praised Costa’s stature and physical style of play which “suits the Premier League down to the ground” in the same role that Didier Drogba previously played at Chelsea, an opinion also voiced by the league’s top scorer of all-time, Alan Shearer. Costa has also been attributed with a greater ability to keep possession of the ball than any Chelsea striker since Drogba first left the club in 2012. That same year, Henry Winter of The Telegraph noted that Costa “…has the technique, the strength and the burst of acceleration to destroy defences.”

Costa has been the source of much controversy in his career due to confrontations with opponents, and has received multiple violent conduct charges from The Football Association of England. Opposing managers have also opined that Costa himself intends to provoke his opponents. Danny Murphy of Match of the Day has stated that Costa is targeted by players who “wind him up,” but he “remains calm”, and is justified to taunt opponents who taunt him. Pat Nevin, a former Chelsea winger, believes that Costa’s style of play is likely to cause himself “a few injuries.” In August 2014, he was criticised by Everton manager Roberto Martínez for taunting Everton’s Séamus Coleman following his own goal, and stated Costa needed “to understand the ethics” of the Premier League. In October 2014, he clashed with Slovakia’s Martin Škrtel in a Euro 2016 qualifier.

With reports speculating that Costa wanting to leave Chelsea, Costa affirmed on 2 June 2015 after Chelsea’s post-season tour that he had no desire to leave London, saying, “It’s always a bit more difficult in the first season for adaptation, but I have no reason to leave this place, I love it, the fans love me, and I want to stay. It’s really good to come in the first season [to Chelsea] and win two things [the Premier League and the League Cup titles]. Next year I’ll be ready to come back and, hopefully, win a couple more trophies.”

Costa, Oscar and Fàbregas were targeted by Chelsea supporters as the players whose poor form led to the dismissal of popular manager José Mourinho in December 2015. Costa scored twice in the first game under interim replacement Guus Hiddink, a 2–2 home draw against Watford. Costa, who played in a protective mask after breaking his nose in training, improved his form under the Dutchman, scoring seven times in his first eight games under the new management.

In January 2015, following two stamp incidents involving Costa and Liverpool players for which Costa received a three-match ban by the FA, Liverpool manager Brendan Rodgers stated that he thought Costa had fouled his players when “he could easily have hurdled over the player” and “there’s no need to do it”. Costa described his style of play as “strong but noble”, and refuted allegations that he deliberately aims to injure opponents.

In late 2015, Costa was the subject of scrutiny for his comparatively poor start to his second season at Chelsea and his low scoring rate for Spain. French newspaper L’Equipe named Costa as the most hated footballer in December 2015, based on his provocative and violent behaviour.

On 12 March 2016, Costa received his first red card in a Chelsea shirt near the end their 2–0 FA Cup quarter-final defeat to Everton for confronting opponent Gareth Barry. Footage appeared to show Costa biting Barry during that confrontation after clashing heads. Earlier in the match, Costa appeared to spit in the direction of the referee after he was yellow carded for a clash with Barry. Later, both Costa and Barry denied that the bite occurred. Costa’s two-match ban was extended to three, and he was fined £20,000. On 2 May, as Chelsea drew 2–2 against Tottenham to deny them the title, Costa was gouged in the eyes by Mousa Dembélé during a mass brawl; the Belgian received a retrospective six-match ban.

On 15 August 2016, Costa scored a late winner against West Ham United to give Chelsea a 2–1 win in their season opener. During the match, he caught opposing goalkeeper Adrián with a late challenge when already on a yellow card, but did not receive a second yellow and went on to score the winner; Adrián stated after the match that he was fortunate not to be seriously injured. On 15 October, he scored in a 3–0 over reigning Premier League champions Leicester City, and on 20 November Costa became the first player to reach ten league goals for the season, with the only one of the game at Middlesbrough. With two goals and two assists for league leaders Chelsea, he was voted Premier League Player of the Month for the second time in November 2016, with his manager Antonio Conte picking up the equivalent.

On 5 September 2016, Costa scored his first international goals for nearly two years, in an 8–0 win over Liechtenstein at the Estadio Reino de León for Spain’s opening match of 2018 World Cup qualification, the first being a header from a free-kick by his former Atlético teammate Koke. In May 2018, Costa was called up to Spain’s squad for the 2018 FIFA World Cup. In their opening game on 15 June in Sochi, he scored his two first World Cup goals to help Spain secure a 3–3 draw against Portugal. Five days later, he scored the only goal of the match against Iran.

In January 2017, Costa fell out with Conte and was dropped from the team, amidst interest from the Chinese Super League. A potential move to Tianjin Quanjian F.C. was curtailed by the league limiting the number of foreign players in each team. He returned to Chelsea’s starting line-up on 22 January, opening a 2–0 win over Hull City, his 52nd goal on his 100th appearance. Costa was Chelsea’s top scorer with 20 goals as they regained the Premier League title. On 27 May, he scored an equaliser in the 2017 FA Cup Final against Arsenal, a 2–1 loss.

In June 2017, Costa was told by Conte that he was not part of his plans for the coming season and that he was free to move to another team via text message. Although Costa was linked to potential moves to the likes of Milan, Monaco, and Everton, he stated that he would only be open to moving back to his former team Atlético Madrid. Costa attempted to find a legal solution through his lawyer in pushing for a move back to Madrid, and said that Chelsea were treating him like a “criminal” by demanding a high transfer fee for his exit. He was excluded from training with the first-team, but was named in the Premier League squad, yet left out of the Champions League squad.

On 21 September 2017, Chelsea announced that Costa would return to Atlético at the start of the next transfer window in January 2018. On 26 September 2017, it was announced that after passing medical tests Costa signed a contract with Atlético. He was registered and became eligible to play after 1 January 2018, due to a transfer ban imposed on Atlético.

On 3 January 2018, he scored on his return game against Lleida Esportiu in a Copa del Rey Round of 16 game, just five minutes after being substituted on for Ángel Correa in the 64th minute. Three days later in his first league game back, he started in a 2–0 win over Getafe at the Wanda Metropolitano and scored the second goal. However, having already been cautioned for a stray elbow on Djene Dakonam, he was cautioned for a second time for charging into the stands to celebrate his goal, thus being sent off. ESPN FC credited Costa as being a key element in Antoine Griezmann’s return to form, opining that Costa’s “physical presence at centre-forward has understandably distracted opposition defenders quite a lot. Griezmann has now taken up a roaming No. 10 role, with freedom to go where he feels best”; Atlético manager Diego Simeone namechecked three of Atlético’s players in particular–Costa, Koke, and Filipe Luís–who had helped Griezmann perform.

Costa’s size, technique, and strength, coupled with his link-up play and ability to hold up the ball with his back to goal allow him to be an effective target-man; moreover, his constant movement and powerful running in the centre-forward role allows him to distract opponents and in turn create space for teammates. Although he was initially known to be inconsistent in the earlier part of his career, due to his low goalscoring rate, he later established himself as a good finisher as his career progressed, which along with his composure in front of goal and ability inside the penalty box, made him a prolific goalscorer, and even saw him regarded by several pundits and managers as one of the best strikers in the world at his peak. In 2018, Simeone lauded Costa for the “enthusiasm” and “aggression” he brings to Atlético Madrid, as well as his “speed, decisiveness, and physical strength.”

In April 2019 he was handed an 8 match ban for abusing a referee. On 18 June 2020, Costa marked his 200th club appearance for Los Colchoneros when he started in a huge 5–0 away win against Osasuna. Costa scored his fifth goal of the season in 1-0 home win against Real Betis to ensure his team a top 4 finish and qualification for next season’s UEFA Champions League.