He played as a central midfielder for English club sides Nottingham Forest, Newcastle United, Tottenham Hotspur, Aston Villa, and Queens Park Rangers, scoring a career total of 39 goals from 341 league appearances.

Hampered by several serious injuries, Jenas failed to reach the career heights expected of him, although he remained at the top level, moving to Tottenham in 2005 for £7 million, with whom he won the Football League Cup in the 2007–08 season.

While still recuperating from his final injury, he moved into media work as a pundit, a role which he continued beyond retirement, including for the BBC on Match of the Day, as well as BT Sport.

Newcastle United, investing in youth, paid a transfer fee of £5 million for Jenas and he became the second most expensive teenager in British football after Robbie Keane.

[14] After the 2001–2002 season Jenas first experienced international tournament football, when, being in the England squad, he was involved in the U21 European Championships[14] held in Switzerland.

[15] Jenas failed to repeat his initial form with the club and his two subsequent seasons were disappointing considering his early promise; he was known for his strong "box-to-box" play and ability to score from midfield.

At Newcastle United he played alongside international footballers such as, Laurent Robert, Gary Speed, Alan Shearer, Shay Given, Nolberto Solano, Patrick Kluivert and Kieron Dyer.

He marked his return from a 13-match absence through injury by scoring the second goal in Tottenham's 3–1 FA Cup fourth round win over Southend United.

[19] Under Juande Ramos, Jenas' form improved greatly and he initially produced occasional impressive performances, partly due to the new regime but also from some personal words of encouragement from the Spaniard.

[20] Jenas played in the 1–1 draw and the 5–1 victory over rivals Arsenal in both legs of the semi-finals of the League Cup, scoring the opening goals in both matches.

[23] Jenas eventually made his debut for Villa on 5 November, after a series of niggling injuries, coming on as a second-half substitute against Norwich City.

While playing, he tripped over his own feet and suffered a ruptured Achilles tendon injury in a game that saw him, Shay Given and Javier Hernández all leave on stretchers.

[28] On the final day of the January 2013 transfer window, Queens Park Rangers signed Jenas on an 18-month contract for an undisclosed fee from Tottenham, to be re-united with former manager Harry Redknapp.

[33] After making 28 appearances for QPR in the Championship, Jenas suffered a ruptured anterior cruciate ligament (ACL) during a training session in April 2014, which ruled him out for the rest of the season.

[38] Jenas formally announced his retirement from football on 7 January 2016 on BBC Radio 4's Today programme, having been unable to recover fully from his knee injury.

[36] On the question of whether or not he had underachieved in his career given his talent at a young age, he answered "yes and no", arguing that he was happy with what he had done, but that he had been held back both by injuries and the shock of losing Bobby Robson as his manager at Newcastle, which "was bigger [to him] than people think it was".

[36] After Jenas was released by QPR, he moved into television as a freelance pundit, firstly as an analyst for ITV Sport's coverage of the 2014–15 UEFA Europa League.

[41] In 2015, Jenas appeared as part of Channel 4's Time Crashers, a reality television programme in which celebrities were assigned the tasks of living in different historical eras.

[45] In December 2023, it was announced Jenas would serve as lead presenter for TNT Sports for the UK coverage of the FIA Formula E World Championship starting from the 2023–24 season.

[9] Jenas and a friend set up the Aquinas Foundation, which offers football tickets to truant students at disadvantaged schools in Nottingham and London if they can achieve a 100% attendance.