Rudi Völler, sporting director of Bayer Leverkusen, has praised Hernández for his keen positioning in front of goal, saying: “he certainly doesn’t win every tackle but he has an incredible sense of where the ball will end up”. Former Manchester United manager Sir Alex Ferguson described Hernández as two-footed, very quick, in possession of a good spring, and a natural goalscorer. Ferguson also said Hernández’s style reminds him of former United striker Ole Gunnar Solskjær – the so-called “baby-faced assassin” who scored the injury time winner against Bayern Munich in United’s 1999 Champions League triumph. Hernández’s former teammate Jesús Padilla described him as “amazing in the air” despite his height. Due to his small stature, he is extremely quick and agile, also possessing good technique.

At the age of nine, Hernández joined C.D. Guadalajara and signed his first professional contract when he was 15. He was set to play in the 2005 FIFA U-17 World Championship, but an injury sidelined him from the team that ultimately won the championship. Whilst playing football professionally, Hernández was also taking business administration classes at Universidad del Valle de Atemajac. Hernández has held both Hugo Sánchez and Rafael Márquez as his football idols growing up.

Hernández began playing with Chivas’ lower division team, Chivas Coras in Tepic, Nayarit in the 2005–06 season. He made his debut for Chivas in the 2006 Apertura in a win over Necaxa at Estadio Jalisco. With the score at 3–0, Hernández came on as a substitute for Omar Bravo in the 82nd minute, before scoring the fourth goal of the game five minutes later. It was his only goal in seven appearances in 2006–07. He made a further six appearances in 2007–08 without scoring.

Hernández made ten appearances in the 2008 Apertura without scoring, but he scored four goals in fifteen appearances in the 2009 Clausura. In the 2009 Apertura, Hernández finished as the joint-third top scorer, with eleven goals in seventeen appearances. He started the 2010 Torneo Bicentenario with eight goals in five games. He finished as a joint-leader in the goalscoring chart for the 2010 Torneo Bicentenario, with ten goals in eleven games and after spent 5 matches without playing because of an injury he suffered.

Manchester United were first made aware of Hernández in October 2009; a scout went to Mexico that December and reported positively after watching a few games. Because of Hernández’s age, the club originally planned to wait before making a move to sign him, but his potential involvement with the national team at the World Cup rushed the club into making a bid. United’s chief scout, Jim Lawlor, was sent to Mexico for three weeks in February and March to watch Hernández and filed another positive report on him, before the club solicitor went over to Mexico to finalise the paperwork.

On 30 September 2009, Hernández made his debut for Mexico against Colombia, where he made an assist in a 2–1 loss. On 24 February 2010, Hernández scored two goals against Bolivia and had an assist for Braulio Luna’s goal. On 3 March, Hernández scored a header against New Zealand, giving Mexico the lead in a 2–0 victory. On 17 March, Hernández scored his fourth international goal to give Mexico a 2–1 victory over North Korea. On 26 May, he scored a consolation header against the Netherlands in a 2–1 loss. On 30 May, Hernández scored yet again, netting twice in a 5–1 victory over Gambia.

On 8 April 2010, Hernández agreed a deal to sign for Manchester United for an undisclosed fee, subject to a work permit application. The previous day, Hernández had been present at Manchester United’s Champions League quarter-final win over Bayern Munich at Old Trafford. The deal was conducted in complete secrecy; Hernández’s agent was kept in the dark, as was his grandfather Tomás Balcázar, who thought Hernández was going on a trip to Atlanta in the United States. As part of the deal, United played a friendly against Chivas to open the Mexican club’s new stadium on 30 July. On 27 May, the work permit was granted, allowing the transfer to be made official on 1 July.

Hernández made his United debut on 28 July, coming on as a 63rd-minute substitute for Nani in the 2010 MLS All-Star Game at the NRG Stadium, Houston; he scored his first goal for the club 18 minutes later, lobbing the ball over Nick Rimando from just outside the area after a long through-ball from Darren Fletcher. Two days later, Hernández scored against Manchester United while playing in a friendly for his old club, Chivas, scoring the inaugural goal at the recently constructed Estadio Omnilife; he started the game in a Chivas jersey and scored after just eight minutes. He switched sides at half-time, but he was unable to prevent a 3–2 defeat for Manchester United. He scored for the third pre-season game in a row as he netted in a 7–1 victory over a League of Ireland XI at the newly built Aviva Stadium on 4 August.

Hernández made his competitive debut on 8 August and scored his first goal in the process, netting United’s second of a 3–1 victory over Chelsea in the 2010 FA Community Shield. He came on at the start of the second half and got on the end of a pass from Antonio Valencia before the Mexican’s shot deflected off his own face and into the net. On 16 August, Hernández made his Premier League debut as he replaced Wayne Rooney in the 63rd minute of their 3–0 home victory over Newcastle United. He scored his first Champions League goal on 29 September, coming off the bench to score the only goal in an away win over Valencia. He scored his first league goal for United in a 2–2 home draw against West Bromwich Albion on 16 October. Eight days later he scored his first brace for the club, also his first away league goals, in a 2–1 away win over Stoke City. Two days on from this display, he came off the bench to score a last-minute winner, his first ever League Cup goal, in a 3–2 win over Wolves which sent them through to the quarter-finals where they were then knocked out by West Ham United. On 1 January 2011, he came off the bench to head the winning goal in a 2–1 away win over West Bromwich Albion. Hernández became the top scoring Mexican in Premier League history after opening the scoring in a 2–1 home victory over Stoke City on 4 January.

Hernández scored another goal in his first match for Mexico since the World Cup, in a friendly against world champions Spain on 11 August 2010. He scored after just 12 minutes of the match, but David Silva equalised for Spain in the last minute of play to claim a 1–1 draw. Hernández scored his and Mexico’s first international goal of 2011 as he opened the scoring in a 2–0 win over Bosnia and Herzegovina on 9 February. On 26 March, Hernández scored two goals in an international friendly against Paraguay. He first connected with a pass from Pablo Barrera in the sixth minute of the match, before scoring off a low cross in the 29th minute, three minutes after teammate Andrés Guardado had made the score 2–0. He exited to a standing ovation in the 65th minute.

Hernández is the son of Javier Hernández Gutiérrez, who played for three clubs in Mexico and was a member of the Mexico squad at the 1986 FIFA World Cup. Hernández Gutiérrez quit his job as manager of Guadalajara’s reserve side in order to watch Hernández play in the 2010 World Cup in South Africa. Hernández is also the grandson of Tomás Balcázar, who also played for Guadalajara and played for the national side in the 1954 FIFA World Cup.

On 8 May, Hernández scored the opening goal in a 2–1 home win over Chelsea after just 36 seconds to leave United one point away from winning the title. The goal against Chelsea made him the first player since Ruud van Nistelrooy in the 2001–02 season to score 20 goals for the club in his debut season. Hernández capped his debut season with Manchester United by winning the Sir Matt Busby Player of the Year award on 18 May which was voted for by the fans. On 28 May, Hernández played all 90 minutes in the 3–1 defeat to Barcelona in the Champions League Final. On 5 July 2011, the International Federation of Football History and Statistics named Hernández as the “World Goalgetter 2011”, with 13 goals, ahead of other players such as Cristiano Ronaldo, Giuseppe Rossi, and Lionel Messi.

After participating in the 2011 CONCACAF Gold Cup with Mexico, Hernández returned to Manchester United to begin pre-season training in New York ahead of the 2011 MLS All-Star Game. On 26 July 2011, he was taken to the hospital after suffering a minor concussion after he was hit on the head with a ball during a training session; he was cleared the next day, but did not take part in the game.

On 28 July 2011, it was reported that Rafael Ortega, the doctor at Chivas, informed Manchester United that Hernández was suffering from a pre-existing neurological condition. Ortega also explained that Hernández had suffered from “acute migraines and “headaches” as a teenager. He did not participate in any of United’s pre-season matches, nor the 2011 FA Community Shield. He also missed United’s opening game of the season against West Bromwich Albion.

Hernández made his first appearance in the 2011–12 season on 22 August in a 3–0 win against Tottenham Hotspur, coming off the bench for Danny Welbeck in the 79th minute. He returned to the starting lineup on 10 September against Bolton Wanderers, scoring twice in a 5–0 victory. On 15 October 2011, Hernández came off the substitutes bench to net a crucial equaliser against Liverpool at Anfield in a 1–1 draw. In the 81st minute Hernández gambled on Danny Welbeck’s flick on from a corner to steal in and head the equaliser.

On 5 June 2011, he scored a hat-trick, the first in his career, in a 5–0 win against El Salvador. On 9 June 2011, he scored two goals, in the 36th and 76th minutes against Cuba. On 18 June 2011, Hernández scored the winner in a 2–1 win over Guatemala to send Mexico to the semi-finals. On 22 June 2011, he helped Mexico reach the Gold Cup Final after a 2–0 win over Honduras in extra-time, where he scored Mexico’s second goal in the 99th minute. Hernández was the Gold Cup’s top scorer with seven goals and was named the most valuable player of the tournament, in addition to helping his team to a 4–2 victory in the Final against the United States.

On 31 January 2012, Hernández scored his first goal since November, and his seventh goal of the season in a 2–0 league win at Old Trafford against Stoke City, scoring the first of two penalties. Hernández continued his scoring form on 5 February at Stamford Bridge against Chelsea, scoring the third goal of a three-goal comeback draw, heading in a cross from Ryan Giggs. On 16 February, Hernández scored his first goal in the Europa League, in a 2–0 away win against Ajax in the round of 32. He scored again in the second leg at Old Trafford on 23 February, but this time in a 2–1 home defeat. However, United still won the tie 3–2 on aggregate. On 18 March, Hernández scored twice in a 5–0 win over Wolverhampton Wanderers.

Hernández began his third season with United on 2 September 2012, coming on as a 72nd-minute substitute for Danny Welbeck in a 3–2 win against Southampton. On 15 September, he was named in the starting eleven for the match against Wigan Athletic, playing all 90 minutes. Despite having a penalty saved in the fifth minute by Wigan goalkeeper Ali Al-Habsi, Hernández scored his first goal of the season, as well as assisting in teammate Nick Powell’s goal in a 4–0 victory. On 23 October, Hernández netted a brace in a 3–2 comeback win against Braga in a Champions League group stage match after United had gone down 2–0 in the first half. Five days later, he scored the winner against nine-man Chelsea in a controversial 3–2 win after he was deemed to have been in an offside position when scoring the goal.

On 10 November 2012, Hernández came on as a second-half substitute and scored two goals as United came from 2–0 down to beat Aston Villa 2–3 at Villa Park. At the end of the match, Hernández claimed the hat-trick, but replays showed that his shot for United’s second goal was hit wide until turned into his own net by Villa defender Ron Vlaar. On 24 November, he scored his fifth league goal of the season in a 3–1 home win over Queens Park Rangers. On 26 December, Hernández scored United’s fourth goal in the final minutes in a 4–3 win over Newcastle United at Old Trafford. He then began 2013 by scoring a brace against Wigan on 1 January, helping United to a 4–0 victory. On 26 January, Hernández would go on to score another brace, this time during an FA Cup match against Fulham which United won 4–1.

On 26 May 2012, Hernández became the Mexican ambassador for UNICEF, making him the third Mexican to serve this position, following César Costa and Julieta Venegas in 2004 and 2009 respectively. As ambassador, he will participate in a number of activities to encourage children and teenagers to not abandon their education. He was commemorated in a news conference, where he said he felt “proud and committed”.

In another FA Cup match against Reading on 18 February, Hernández scored in the 72nd minute, giving United a 2–0 lead. His goal would end up being a deciding factor as United went on to win the game 2–1. Although he started in United’s 2–0 Premier League victory against QPR on 23 February 2013, he did not score in the match and he didn’t score again until 10 March in another FA Cup match against Chelsea which ended in a 2–2 draw. Hernández opened the scoring in manager Sir Alex Ferguson’s final home game at Old Trafford against Swansea City. After a free kick was not cleared, he slotted in from six yards in the first half to put United 1–0 up, in a game they went on to win 2–1. Hernández scored United’s last goal of the season and the final goal of the Ferguson era, when he tapped in a cross from close range in a 5–5 draw away at West Bromwich Albion on the final day.

Hernández scored his first goal of the season under new manager David Moyes on 25 September 2013, netting the only goal of a home win over rivals Liverpool in the third round of the League Cup. On 26 October, with his first league goal of the campaign, he headed the winner as they came from behind to defeat Stoke 3–2 at Old Trafford. Three days later, he recorded a brace – starting with a penalty – in a 4–0 win against Norwich City in the next round of the League Cup. In the tournament’s semi-finals, his goal from Adnan Januzaj’s cross in the last minute of extra time forced a penalty shootout, which United lost to Sunderland.

Hernández is a devout Roman Catholic. He is well known for his pre-game ritual where he gets on his knees and prays which he performs before most games. On 27 June 2013, EA Sports announced that they had featured Hernández on the North American cover of FIFA 14, alongside global cover star Lionel Messi.

On 1 September 2014, Hernández signed for Real Madrid on a season-long loan deal, with an option of a purchase at the end of the loan. He underwent a medical and signed the contract that same day.

He scored the winning goal on 22 April 2015 in the 1–0 win over Atlético Madrid, which sent Real Madrid into the semi-finals of the Champions League. Four days later, Hernández scored a brace in Madrid’s 2–4 away win over Celta de Vigo.

On 29 August 2015, it was reported that Manchester United manager Louis van Gaal had told Hernández he could leave the club before the closure of the transfer window. Although with one year of his contract still remaining, it was unclear with scale of transfer fee United would demand for him.

On 31 August 2015, it was announced Hernández signed a three-year contract with Bundesliga club Bayer Leverkusen for an undisclosed fee, reportedly £7.3 million.

On 1 July 2015, Hernández sustained a broken collar bone during a friendly match against Honduras, ruling him out of the 2015 CONCACAF Gold Cup, which Mexico went on to win.

In October 2015, Hernández was called up for the CONCACAF Cup – a play-off match to determine CONCACAF’s entry into the 2017 FIFA Confederations Cup – against the United States. Mexico defeated the U.S. 3–2 after extra time at the Rose Bowl, with Hernández opening the score after ten minutes.

On 30 January 2016, in Bayer’s second match after the winter break, Hernández scored twice in a 3–0 defeat of Hannover 96 to register his 20th and 21st goals of the season. Two days later, he was named for the third time Bundesliga Player of the Month.

Hernández scored and provided an assist in Leverkusen’s 2–1 win over SC Hauenstein in the first round of the DFB-Pokal on 21 August 2016. Two days later, it was reported that Hernández would miss Bayer’s opening match of the season against Borussia Mönchengladbach after sustaining a broken hand. On 17 September, Hernández scored his first goal of the Bundesliga season at Eintracht Frankfurt, however he missed a chance to equalise late from the penalty spot in the 2–1 loss. The following week at FSV Mainz 05, Hernández collected a perfect hat-trick that included a stoppage time winner, the third hat trick of the Bundesliga season. He was later named Bundesliga Player of the Month for September.

Hernández was included in Mexico’s 23-man squad that would participate in the Copa América Centenario tournament. On 5 June 2016, he played 83 minutes in the 3–1 victory over Uruguay, and scored the first goal in Mexico’s 2–0 win over Jamaica. The goal took Hernández’s tally to 45, one goal shy of tying Jared Borgetti’s national team record.

On 28 January 2017, Hernández scored Bayer Leverkusen’s second goal in the 2–3 loss to Borussia Mönchengladbach, ending his eleven-match scoreless streak. On 21 February, following the match against Atlético Madrid, Hernández became the Mexican player with the most appearances in the Champions League with 47, surpassing Rafael Márquez’s previous record of 46 appearances.

On 24 July 2017, Hernández joined English club West Ham United for an undisclosed fee, reported to be around £16 million, signing a three-year contract. He was given the number 17 jersey. He made his debut for the West Ham on 13 August, playing all 90 minutes in the 4–0 defeat against his former club Manchester United at Old Trafford. The following week, Hernández scored his first two goals for West Ham in the 3–2 loss to Southampton.

On 12 May 2017, Hernández was included in the national squad that would play in the FIFA Confederations Cup in Russia. On 27 May, Hernández became Mexico’s all-time top goalscorer with 47 goals when he scored in a friendly against Croatia. In Mexico’s Confederations Cup debut, he scored Mexico’s first goal in an eventual 2–2 draw against Portugal on 18 June, scoring a low header from a Carlos Vela cross.

In November, Hernández sustained a hamstring injury while on international duty with Mexico, and it was reported that he would be ruled out from activity for up to two weeks. Following the sacking of Slaven Bilić and the appointment of David Moyes as manager, there were fears Hernández would be excluded at West Ham as he was at Manchester United. In response, Moyes referred to him as a “top goalscorer,” and “a brilliant finisher.” During the winter transfer window there were reports Hernández would exit the club after only six months, being linked with a move to Turkish club Beşiktaş as well as a possible return to Manchster United. On 20 January 2018, he came off the bench to score the equalising goal for West Ham in their 1–1 league draw against Bournemouth, scoring his first goal since October. Following the match Moyes praised Hernández’s performance, saying “we needed him today.” On 8 April, in a league match against Chelsea, he scored a 73rd-minute goal to make the score 1–1, marking the ninth time he had scored against the club.

On 28 August 2018, Hernández scored West Ham’s third goal in injury time of a 3–1 victory over AFC Wimbledon in the second round of the EFL Cup. In September, West Ham manager Manuel Pellegrini declared that Hernández was suffering from glandular fever, causing him to miss out various matches. He would recover and return to training in October. On 3 November, he scored his first Premier League goal of the season in West Ham’s 4–2 victory over Burnley.

On 27 March 2018, Hernández earned his 100th cap in a friendly match against Croatia.

On 22 February 2019, Hernández scored the equalising goal in West Ham’s eventual 3–1 win over Fulham; on initial viewing, it looked like he had headed the ball in from a yard to score, however replays of the goal appeared to show the ball rebound off of Hernández’s arm to put the ball into the net. It was also his 50th career Premier League goal, becoming the first Mexican to reach the milestone. He would get on the scoresheet again on 16 March, coming on as a second-half substitute and scoring twice—including the stoppage-time winner—to secure a 4–3 league victory over Huddersfield.

Prior to the start of the season, he was given the number 9 shirt. Hernández scored his first goal of the 2019–20 Premier League season on 17 August 2019 as West Ham drew 1–1 with Brighton at Falmer Stadium. On 30 August, Hernández handed in a transfer request to West Ham and flew to Spain to complete a medical ahead of a proposed €8 million move to Sevilla.

On 2 September 2019, Hernández joined La Liga club Sevilla for an undisclosed fee, reported to be £7.3m, signing a three-year contract. He made his league debut on 15 September in an away match against Alavés, coming on as a 70th minute substitute in Sevilla’s 1–0 win. Four days later, in a Europa League group stage match against Azerbaijani side Qarabağ FK, Hernández scored a free kick, the first in his career, in his side’s 3–0 victory. On 27 October, he scored his first goal in La Liga with Sevilla in a 2–0 victory against Getafe.

In January 2019, Hernández and his wife Sarah Kohan, an Australian model of Romanian origins and travel blogger, announced on Instagram that they were expecting their first child. On 16 June 2019, their son, Noah, was born.

On 21 August 2020 Hernandez won the 2019-20 UEFA Europa League despite having left he is still credited with the victory due to participating in 2 matches.

On 21 January 2020, Hernández signed a three-year contract with Major League Soccer club LA Galaxy, and became the highest paid player in the league. He made his MLS debut on 29 February in a 1–1 draw against Houston Dynamo, captaining the team and playing the entirety of the match. On July 13 he scored his first goal for the club against Portland Timbers which ended in a 2–1 loss.