Boa Morte made his debut in English football for Arsenal when he became one of Arsène Wenger's first signings for the club, joining for a fee of £1.75 million.

In his season at The Dell, he made a total of 17 appearances, mostly as substitute, with one goal – a thundering left foot drive at Watford in a 2–3 defeat on 28 December 1999.

[10][11] His contributions to the championship-winning season resulted in him being signed permanently in June 2001 (on a fee of £1.7 million paid to Arsenal), despite Southampton's attempts to bring him back after the expiry of the loan arrangement.

[12] Boa Morte accused Everton forward Duncan Ferguson of racial abuse after an FA Cup fourth round match in January 2004.

[17] Boa Morte signed for West Ham United in January 2007 on a three-and-a-half-year contract for an undisclosed fee, which was believed to be around £5 million.

[18] He played his first game for the Hammers in an FA Cup tie against Brighton & Hove Albion, setting up two goals and on 13 January 2007 in the Premier League against former team Fulham.

West Ham were playing in the Premier League Asia Trophy in Beijing when Boa Morte got his studs stuck in the ground, twisted his knee and suffered an anterior cruciate ligament injury.

[23] In June 2010, West Ham Chairman David Sullivan announced that Boa Morte had been offered a new deal as his contract was due to finish at the end of the 2009–10 season.

[24] On 17 June 2010, Boa Morte signed a new two-year contract saying that he was looking forward to working with new West Ham manager, Avram Grant for the next two seasons.

[9] Boa Morte made his debut for the Portugal national football team on 25 April 2001 in a friendly 4–0 defeat away to World and European champions France, as an 87th-minute substitute for Rui Jorge.

His only goal came in a 5–1 home win against Angola on 14 November that year,[citation needed] a game which had to be abandoned when the African team were reduced to six players on the pitch.

His former Fulham teammate Louis Saha publicly called the omission "revolting and scandalous", and advised Boa Morte never to play for Portugal again.

He was sent off early in the second half of a 4–2 loss to Iraq for a kick at Bassim Abbas, in a match that received widespread media coverage due to the ongoing war in the opponents' nation.

[37] Boa Morte was part of Scolari's team that came fourth at the 2006 FIFA World Cup in Germany, playing ten minutes in place of captain Luís Figo at the end of a 2–1 win over Mexico in the final group game.

[55] Boa Morte made a guest appearance as himself in a February 1999 episode of the BBC children's drama series Grange Hill, giving out prizes at a school sports day.

[56] He appeared on the MTV reality series Cribs, showing viewers a relatively modest detached house in Surrey and his Vauxhall Corsa; he said that he had never been in his own garden.