
1998–2003: S Club
At the age of twenty, Stevens became a member of the British pop group S Club 7, which were a BRIT Award-winning British pop group created by former Spice Girls manager Simon Fuller. The group rose to fame via their own BBC television programme and by selling 16 million records worldwide and launching four number one hit singles in the United Kingdom. S Club eventually split up in 2003.
In both 2001 and 2002 she was voted the second Sexiest Woman in the World by UK's FHM readers.
Solo
After S Club were disbanded, Stevens signed a £1.5 million ($2.3 million) solo four-album deal with Polydor Records and re-signed with Fuller. Stevens said that breaking out on her own after success with S Club was difficult: "I think we [S Club] ended up conforming to what people's perceptions were. This one was the ditzy one, this one was the singer, this one was the dancer. And to come out of that and be a whole person has been a real challenge for me. I didn't have my say, really, in the group. None of us did."

Her first solo single, written by Cathy Dennis and produced by Bloodshy & Avant, "Sweet Dreams My LA Ex", was released in September 2003. Taking inspiration from R&B and adult-style pop music, Stevens's debut solo album, Funky Dory, was released later that month. The album was a minor hit, reaching number nine on the UK albums chart. Although it was not a huge commercial success, it gained praise from pop critics; Jamie Gill, in a review for Yahoo! Launch, said that Stevens "eschews the cheap and cheerful approach of her old band for a slinky adult confidence and musical eclecticism."
That December, the album's title track, "Funky Dory" (featuring a sample of the David Bowie song "Andy Warhol" from his album Hunky Dory), was released as its second single and failed to match the success of "Sweet Dreams My LA Ex", peaking at number twenty-four. MusicOMH called it "musically better than "Sweet Dreams My LA Ex" with a hybrid of pop, Latin and even a hint of jazz infusion" but not a good single choice as a single as it lacked anything special and different.
In July 2004, Stevens released the BBC Sport Relief charity single, "Some Girls", which was produced by Richard X. It became a hit across Europe, and reached number two in the UK. HMV.co.uk called the song Stevens's "finest song to date", and Yahoo! Launch commented that "she came to save her career. She ended up saving pop."
Following the success of "Some Girls", Funky Dory was re-released to include "Some Girls" and another new track, a cover of Andrea True Connection's "More More More". "More More More" was issued as a single and peaked at number three in the UK, giving Stevens her third top ten solo single in the UK. At this point, Stevens and her management stepped up promotion, earning her a Guinness World Record for "Most Public Appearances by a Pop Star in 24 Hours in Different Cities" (seven on 8 September-9 September 2004).

In late 2004, Stevens began working on her second solo album, Come and Get It, with producers and songwriters Richard X, Alexis Strum, and Xenomania. The following March, its first single, "Negotiate with Love", was a top ten hit in the UK. "So Good" was released in July 2005 and also peaked at number ten, being hailed as "tastily produced and sassily delivered." In mid 2005, Channel 4 broadcast a documentary which followed Stevens through the summer as she promoted "So Good".
Stevens released Come and Get It in October 2005. The album was less successful than her debut, peaking at number twenty-eight in the UK. Its third and final single was "I Said Never Again (but Here We Are)", which peaked at number twelve in the UK and was commended by HMV.co.uk for its "astonishingly flawless vocal performance" and as Stevens's "most commercially accessible and quirky single since "Some Girls"." It has the song "Je m'appelle Rachel" on it, which was originally written by Shelly Poole as "Je m'appelle Michelle".
In 2007, The Guardian included the album in their "1000 Albums You Must Hear Before You Die" list.
2009–present: New Material
In December 2009, Stevens confirmed plans to release new material. She stated, "It's very early stages at the moment, but I'm going into the studio in the New Year ... all very exciting! I'll keep you all posted with what's going on."

While Stevens was a member of S Club 7, she appeared in five series of S Club shows: S Club 7 Go Wild! Miami 7, L.A. 7, Hollywood 7, and Viva S Club. The group also starred in the feature film, Seeing Double. In 2004, Stevens briefly appeared in Suzie Gold, followed by a minor cameo role in Deuce Bigalow: European Gigolo (2005).
In 2005, Stevens played a character called "Jane-Mary" in a Spider Man charity spoof called Spider-Plant Man for the BBC appearing opposite Rowan Atkinson. In December 2007 it was announced that Stevens would be transformed into a nine-inch high plasticine character for Glendogie Bogey, a new animated comedy for BBC Scotland. Later in 2005, Stevens also played a minor role in Dominic Veall's ITV television drama Flawless playing Lucy Carlts, the sister of Rodger Carlts.
In January 2009, Stevens was reportedly "in talks" to appear in the second series of BBC One's Merlin.
Strictly Come Dancing
In August 2008, it was announced that Stevens would take part in the 2008 series of Strictly Come Dancing, which started on 20 September. She was partnered with professional dancer Vincent Simone, and together they hold the record for the most perfect 10s ever achieved in any series of Strictly Come Dancing, thus beating out other contestants including 2007 winner Alesha Dixon and 2008 winner Tom Chambers. They also hold the record for the Foxtrot, Tango, Argentine Tango and Rumba and even though Stevens is perhaps the most successful contestant in Strictly history, she finished in second place.