Born in Figueira da Foz, Coimbra District, Almeida started playing football for hometown club Naval 1º de Maio, before being signed by Porto still as a junior. He made his Primeira Liga debut in a 2–0 home win over Benfica on 21 September 2003, playing three minutes; unable to settle at first, however, he had loan spells with União de Leiria (with which he had already played in the previous season, also on loan) and Boavista.

Almeida played at every level in international competitions, from the under-15 to the main Portuguese national team. He made his full debut in a friendly match against England on 18 February 2004, in a 1–1 tie, and was also part of the squad that won the 2003 Toulon Tournament, also appearing at the 2004 and 2006 UEFA European Under-21 Championship finals.

Almeida served another loan stint in 2006–07, with a solid first year at the Bundesliga’s Werder Bremen, where he rejoined former Porto teammate Diego. He totalled ten goals in 41 appearances (in all competitions), including one in a 1–2 home loss against Espanyol in the season’s UEFA Cup semi-finals, his shot floating over the goalkeeper and into the net in an eventual 2–4 aggregate defeat; after seeing his chances at Porto definitely cut down with the arrival of strikers Edgar and Ernesto Farías in August 2007, he decided to accept Bremen’s offer for a permanent switch, penning a four-year deal worth €4 million.

In Carlos Queiroz’s second stint as national side coach, Almeida scored in a 4–0 triumph in Malta on 6 September 2008, in the 2010 FIFA World Cup qualifying campaign. His importance diminished in late 2009, after the naturalization of Sporting Clube de Portugal’s Liédson.

Almeida started 2010–11 netting six times in the first ten league games. On 28 November 2010 he took his total to nine, after scoring three in a home win against FC St. Pauli (3–0) – in the dying minutes of the fixture, he was sent off after elbowing an opponent.

On Christmas Eve 2010, after scoring 11 goals in 21 official games for Bremen during the season, Almeida joined Beşiktaş in the Süper Lig, having agreed to a three-and-a-half-year contract for €2 million. On 11 May 2011, he converted his penalty in the shootout as the Istanbul team won the Turkish Cup against İstanbul Başakşehir (4–3, 2–2 after extra time).

Almeida was picked for the finals in South Africa. After the first match, a 0–0 against Ivory Coast, he replaced Liédson in the starting XI for the following match, with both players finding the net in the 7–0 routing of North Korea on 21 June 2010, in Cape Town.

On 7 October 2014, free agent Almeida signed for Serie A newcomers Cesena. However, he struggled at his new club, managing only seven starts and terminating his contract by mutual consent on 20 January 2015. A week later, he joined Russia’s Kuban Krasnodar.

On 8 July 2015, Almeida moved to Anzhi Makhachkala who had just returned to the Russian Premier League. After just six months, both parties parted ways by mutual consent.

On 31 March 2015, Almeida captained Portugal for the first time in his final appearance, a 0–2 friendly loss to Cape Verde in Estoril.

On 16 January 2016, Almeida returned to Germany and signed for Hannover 96 until summer 2017, reuniting with former Werder Bremen boss Thomas Schaaf in the process. He scored in his first appearance seven days later, but in a 1–2 home loss against Darmstadt 98. In February, he received a retrospective three-match ban for an elbow on FC Augsburg’s Dominik Kohr, as the season ended with relegation.

On 18 July 2016, Almeida joined AEK Athens from the Superleague Greece on a two-year contract. He scored twice in the first 15 minutes of his debut, a 4–1 home win over Xanthi on 11 September.

On 26 April 2017, in the return leg of the semi-finals of the Greek Football Cup against Olympiacos, Almeida played as an emergency goalkeeper for the first time in his career, after Giannis Anestis was sent off in the closing minutes of the game. His team eventually advanced to the final on away goals, after a 2–2 aggregate draw.

On 30 August 2017, Almeida’s contract was terminated by mutual consent. The following day he signed a one-year deal with Hajduk Split from the Croatian First Football League, with the option for a further season.

Almeida returned to Portugal after an absence of 12 years in July 2018, at the age of 34. Citing family reasons, he agreed to a two-year contract at Académica de Coimbra. He made his LigaPro debut on 18 August, playing 36 minutes in a 0–1 home defeat against Paços de Ferreira and eventually acting as a goalkeeper after Peterson Peçanha was sent off.

On 6 February 2020, Almeida announced his retirement. He went instantly into coaching Académica’s under-23 team.