Jim Tomlinson was born on September 9, 1966, in Sutton Coldfield, Warwickshire, and grew up in Northumberland. His own account of how he found jazz is that, as a fourteen-year-old in the far north of England with few places to buy records, he followed the rule that a saxophone on the cover meant a purchase. That is how he came to own Getz/Gilberto, made by Stan Getz and João Gilberto. Getz, and in particular the Getz of the bossa nova records, has been a reference point for him ever since.

He studied philosophy, politics and economics at University College, Oxford, playing saxophones and clarinet and running a band as a hobby, and he did not study music formally until his twenties. After graduating he moved toward London's jazz scene and in 1990 enrolled at the Guildhall School of Music and Drama. It was at the Guildhall that he met the singer Stacey Kent, and the two married on August 9, 1991.

On the London scene he worked with the saxophonist Matt Wates, the trumpeter and bandleader Humphrey Lyttelton and the pianist and composer Michael Garrick. His saxophone is on Garrick's For Love of Duke ... And Ronnie, a session with the singer Jacqui Dankworth recorded in London in the mid-1990s and released on Garrick's Jazz Academy label. In the 1990s he also led his own quartet around the United Kingdom. Discogs credits him on alto saxophone and clarinet on four tracks of Bryan Ferry's standards album As Time Goes By (Virgin, October 25, 1999). He is on Kent's first Candid album, Close Your Eyes (1997), and on Between Friends (Calligraph, 2000), recorded March 10 and 22, 2000 with Lyttelton's band, where he is credited on tenor, alto and baritone saxophones and bass clarinet and the cover bills Kent and Tomlinson together.

His own debut, Only Trust Your Heart, came out on Candid on April 18, 2000. He led a quartet of Colin Oxley (guitar), John Pearce (piano), Simon Thorpe (bass) and Steve Brown (drums), with the trumpeter Guy Barker joining on three tracks and Kent singing on three. Brazilian Sketches followed on Candid in the United Kingdom in 2001 and in the United States on April 15, 2003. It is built around Antonio Carlos Jobim songs, with pieces by Marcos Valle, Luiz Bonfá and Cole Porter, and Kent sings on four of the eleven tracks. The Observer named it Jazz CD of the Week, and his own biography adds that it was well received in Brazil. His third album as a leader, The Lyric, was released in 2005 on his own Token label, with later editions on O+ Music in France and on Blue Note in 2011. It is a set of thirteen pieces, standards and bossa nova, on which Kent sings eleven, and it was named Album of the Year at the 2006 BBC Jazz Awards.

Since then his recorded career has run mostly through Kent's. Discogs lists him as producer of her albums from Love Is... The Tender Trap (1998) through Summer Me, Winter Me (2023), and credits him as saxophonist and often flutist on the records themselves. This is the pop-facing, songbook side of his work and it is where his audience is: Kent's Breakfast on the Morning Tram (Blue Note, 2007), which he produced, was nominated for a Grammy Award and sold platinum in France. In 2006 he began writing songs for her with the Nobel Prize-winning novelist Kazuo Ishiguro, who supplies the lyrics; four of their songs are on Breakfast on the Morning Tram, and one of them, "The Ice Hotel," won first prize in the jazz category of the International Songwriting Competition. Their later work together includes songs on Dreamer in Concert (2011), The Changing Lights (2013) and I Know I Dream: The Orchestral Sessions (2017), on which he is credited as producer, conductor and co-arranger. A Kent album released on March 5, 2024, The Summer We Crossed Europe in the Rain, collects the Ishiguro and Tomlinson songs and has him on tenor saxophone on eight of its tracks.

The Brazilian thread kept running. He is the saxophonist on Kent's live album with Marcos Valle, Ao Vivo Comemorando os 50 Anos de Marcos Valle (Sony, 2013), and on her records with the guitarist Roberto Menescal, The Changing Lights and Tenderly (2015). He plays flute on a track of Danilo Caymmi's Jobim tribute (2016), and on the 2014 album Brazil (Erato), on which the French string quartet Quatuor Ébène accompanies Kent and Bernard Lavilliers, Discogs credits him as producer and editor of five tracks and as saxophonist on three. He also plays saxophone on a track of Fernanda Takai's Jobim album O Tom da Takai (2018), produced by Valle and Menescal. Outside the Kent circle, Discogs credits him as co-producer of one track on Francesca Tandoi's Songbook Vol. 1 (Fresh Sound), released in 2026.

As of 2026 he remains Kent's saxophonist and producer. Their album A Time for Love was released on Naïve on April 3, 2026, again with the pianist Art Hirahara. Discogs lists no new album under his own name since The Lyric in 2005, apart from compilations of recordings with Kent.

Tomlinson plays tenor saxophone in the line that runs from Lester Young through Stan Getz, and he names both as models. He has said that the early bossa nova records of João Gilberto, Astrud Gilberto, Jobim and Getz are still the foundation of what he and Kent do. Reviewers have heard that: Bruce Lindsay at All About Jazz wrote in 2011 that his tone is warm and engaging, more relaxed even than Getz's, and Tony Augarde at MusicWeb International wrote in 2006 that he sounds a good deal like Getz, with a mellow sound and supple, fluent improvisation, adding that he would like to hear more of the urgency Getz brought to his bigger records. Augarde also noted that on The Lyric Tomlinson was often held to a single chorus per song while the vocals carried the record, and that is a fair description of his role over most of his career: the counter-voice to a singer, playing behind and around a lyric rather than taking long solos. He also plays flute and clarinet, and he plays Selmer saxophones. Most of his recorded work serves Kent's audience for songbook standards, bossa nova and French song, which overlaps with pop listening as much as with the jazz club, and he is better known as her saxophonist, producer and co-writer than as a bandleader in his own right.