Born in São Bernardo do Campo, Deco spent time at Corinthians as a youngster, competing in the Copa São Paulo de Futebol Júnior for them. In the 1997 edition, Benfica sent Toni to scout the tournament, and he soon noticed Deco, recommending his signing. In June 1997, Benfica purchased his rights from CSA and immediately sent him on loan (along with fellow Brazilian Caju) to their farm team, Alverca. After helping them win promotion to the top tier in 1997–98 season by scoring 13 goals in 32 appearances, he returned to Benfica in July 1998. However, he left for Salgueiros in exchange for Nandinho, who went in the opposite direction. When asked by Nuno Gomes in an interview for FourFourTwo why he did not stay and become a legend at Benfica, Deco said, “Benfica decided, it wasn’t my decision. They didn’t want me. The coach was Graeme Souness at the time. I was young and Benfica needed some players.”

When Deco started his European career in 1997, his first wife Cila, whom he had met three years earlier, moved to Portugal with him. Deco and Cila have two sons, João Henrique and Pedro Gabriel, who now live in Brazil with their mother. A few years later, Deco met Jaciara at a party in Salvador, Brazil, and divorced Cila to live with Jaciara in Porto. They married in April 2005 and now have a son, David, and a daughter, Yasmin. They announced their divorce in March 2008. In 2009, he married to his ex-girlfriend Ana Paula and she gave birth to his fifth child, a daughter, Sofia.

At Salgueiros, Deco was plagued by injuries and only made a few appearances, until Porto purchased him in March 1999, in time to win the league title. His release from Benfica and subsequent success with Porto was considered by António Simões as an “historical mistake”, while Toni stated he saw in Deco, a successor for Rui Costa the club needed since his departure.

On 17 June 2004, Deco told a Portuguese radio station he would almost certainly join English side Chelsea (then coached by José Mourinho) following UEFA Euro 2004. He said a transfer deal between Porto and Chelsea had been all but finalised, and that the only remaining steps were passing a physical examination and signing a formal contract with Chelsea.

However, on 26 June 2004, Deco told the Portuguese sports daily O Jogo he would rather move to Barcelona than follow Mourinho to Chelsea. While Bayern Munich gave up on Deco after the Chelsea deal seemed to have been concluded, it was still uncertain whether the German side would make a new bid. The best offer at that time was a €21 million bid from Barça, but this figure was still €4 million short of the request by Porto’s board of directors. Portuguese newspapers then reported Barça would try to offer Portuguese winger Ricardo Quaresma as part of the exchange in order to ease the deal.

Finally, a deal was achieved between Porto and Barcelona the day after the Euro 2004 final. Barcelona agreed on a €15 million fee in cash, plus the complete rights of Quaresma to Porto, which tagged Quaresma for €6 million. Deco signed a four-year deal with the Catalan side on 6 July 2004.

In Barcelona, some suggested Deco would be completely eclipsed by Brazilian star Ronaldinho (a duo that according to Luiz Felipe Scolari “can make rain fall”). Indeed, many Barcelona fans met the transfer with raised eyebrows, as Deco was considered an attacking midfielder, a department which was already well covered. Instead, coach Frank Rijkaard used him in a three-man midfield, where his tactical knowledge, passing abilities and enormous work rate surprised many. In December 2004, he came second in France Football’s Ballon d’Or 2004 award, losing to Andriy Shevchenko and beating teammate Ronaldinho by six votes.

On 14 May 2005, Deco played in the draw against Levante, which gave Barcelona their 17th La Liga title. He also was named Barcelona’s player of the season in the 2005–06 season.

Deco scored twice in the 2006 Supercopa de España, which Barça won. Deco won the UEFA Best Midfielder Award yet again for his performance in Barça’s UEFA Champions League-winning season, enabling him to join the exclusive group of players that have won the same award more than once with different teams, having won the Champions League previously with Porto. He was also awarded the Golden Ball at the FIFA Club World Cup and the Man of the Match award, despite losing the final to Internacional.

In the 2006 World Cup, Deco scored the first goal in Portugal’s second Group D match against Iran in the 63rd minute prior to Cristiano Ronaldo’s 80th-minute penalty. During the first knockout stage of the competition, Deco received two yellow cards in the match against the Netherlands with the first given for a rash tackle on John Heitinga, suspending him from the quarter-final win against England, as he already picked up a caution in the match with Iran. The win against England in the quarter-final stage led to Portugal’s defeat in the semi-final, which Deco was able to participate in.

On 30 June 2008, Chelsea signed Deco from Barcelona on a three-year contract for €10 million (£8 million). He was the first signing of new Chelsea coach Luiz Felipe Scolari, who was formerly the head coach of the Portugal National Football Team.

Deco scored on his Chelsea debut and his Premier League debut with a 30-yard goal in a 4–0 victory over Portsmouth. Deco followed up his performance by scoring in his second game for Chelsea, a curling free-kick against Wigan Athletic. These performances led to him winning the Premier League Player of the Month award for August. Deco made his UEFA Champions League debut for Chelsea on 16 September. Deco injured himself during a training session, but he returned from the thigh injury on 19 October and came on as a substitute against Middlesbrough. He was sent off in the 3–1 defeat by Roma on 4 November 2008. He then scored a bicycle kick against Bolton Wanderers on 6 December.

After talks with new Chelsea manager Carlo Ancelotti, Deco said he was very happy at the club and wanted to show everyone what he could do. He started on the bench in the 2009 FA Community Shield against Manchester United. Deco himself stepped up to take the winning penalty for Chelsea, but was not allowed as Salomon Kalou was placed before him on the list handed to the referee. Deco had an excellent start to the new campaign. He came on as a second-half substitute in the first match of the new season for Chelsea against Hull City and assisted Didier Drogba, who scored in injury time.

On 6 August 2010, Deco signed a two-year contract with Brazilian club Fluminense on a free transfer, joining former Chelsea and Barcelona teammate Juliano Belletti.

In February 2010, Deco announced he would be retiring from international football after the 2010 World Cup.

On 26 August 2013, Deco retired, ending a 17-year career. The decision came on the day before his 36th birthday. His final match was four days prior, against Goiás. Playing for Fluminense, Deco won the Campeonato Brasileiro in 2010 and 2012.

Deco also failed a drug test during his stay with Fluminense. In 2014, it was found that the result may have been due to a false positive or the contamination of the container of the urine sample. The Brazilian Football Confederation and Deco agreed to settle the case, and Deco was found not guilty of doping.