[3] He began his professional career at Albacete Balompié, making his La Liga debut on 7 November 1993 as a 75th-minute substitute for Alejandro in a 2–3 loss against CD Tenerife at the Estadio Carlos Belmonte,[4] and he made one more appearance that season, also from the bench.

[5] On 23 October 1994, soon after coming on as a first-half replacement for Alberto Monteagudo, Morientes scored his first professional goal, opening a 2–0 home win over Racing de Santander.

[6] He got his first start a week later in a 1–5 loss at RCD Español,[7] and finished the campaign with a total of five goals in 20 league games; additionally, he found the net in each leg of a 3–2 aggregate win over holders Real Zaragoza in the last 16 of the Copa del Rey.

[15] He finished second in the top scorers list, tied with Patrick Kluivert and behind Deportivo de La Coruña's Diego Tristán,[16] as the Merengues were successful in winning the Champions League after beating Bayer 04 Leverkusen – he played in the final and received a third winners medal.

He eventually fell down the pecking order of strikers to Guti and Javier Portillo[18] and, during a February 2003 home win against Borussia Dortmund – 2–1 in the Champions League second group stage – was involved in a highly publicised spat with manager Vicente del Bosque, with the player allegedly insulting the coach after being called to enter the pitch as a third replacement in the dying minutes;[19][20] in the winter transfer window, despite continuous rumours of moves to Tottenham, Zaragoza, AS Roma and AC Milan, he remained at the club for remainder of the season as the side went on to win the league, with the player making a total of 19 appearances (with three starts) and scoring five goals.

[27] After returning to Real Madrid at the start of the 2004–05 campaign, Morientes' hopes of forcing his way into the squad were further dampened with the arrival of Michael Owen from Liverpool.

[30] Morientes made his debut for Liverpool on 15 January 2005 against Manchester United, starting in a 0–1 home loss to the rivals – BBC Sport described his performance as "quiet".

[36] On 21 March 2006, he scored in a 7–0 rout of Birmingham City in the quarter-finals of the FA Cup, finishing Steven Gerrard's cross three minutes after entering in place of Peter Crouch.

[43] He linked up well with David Villa[44] and scored 12 goals in 24 games, and was also team-top scorer in the Champions League with seven; his good form throughout the season also earned him a recall to the national side.

The campaign, however, was disappointing, as the Che were knocked out of the Champions League after finishing fourth in the group, and manager Quique Sánchez Flores was dismissed following a poor run of form.

Having begun the following campaign as an unused substitute in Valencia's first league game, and only coming on from the bench in the second, Morientes was handed his first start in a UEFA Cup match against C.S.

[50] His increasing age and the form of Villa and Juan Mata, however, led to only a handful of appearances in the league; as they were ousted in the round of 32, he still finished as their top scorer in European competition at three goals in seven matches.

[51] On 27 July 2009, Morientes agreed to a deal at France's Olympique de Marseille on a free transfer for one year, reuniting with former Monaco boss Didier Deschamps.

[59] Morientes was a reliable performer for the Spain national team since 1998, scoring a brace in the first five minutes of his debut against Sweden on 25 March[60] and adding a further two in each of his next two games, against Northern Ireland[61] and Bulgaria respectively.

[76] Morientes competed in the third season of Mask Singer: Adivina quién canta as "Gorila", being declared joint winner with Ana Torroja as "Ratita".