After a successful audition Stevens became a member of the British pop group "S Club 7", selling sixteen million records worldwide and achieving four number hit singles in the United Kingdom. The group was disbanded in 2003 due to undisclosed reasons. Stevens became the first member of the band to sign a multi-million dollar recording contract and released her first solo single, "Sweet Dreams My LA Ex", in late 2003, reaching number two on the UK singles chart. Her first album did not fare so well, peaking at disappointing number nine on the UK albums chart and quickly disappearing. Stevens' follow-up single also failed to gain much attention. Critics began to write her off as a one-hit wonder until she came back with the song "Some Girls" (2004) which quickly became a hit in the UK, peaking at number two. In late 2005 Stevens released her second solo album, which failed to perform well on the pop charts, becoming a commercial failure even though it was praised by the pop music press and other outlets, such as The New York Times.

Stevens was born in Southgate, London of Jewish heritage. Her now-estranged father, Michael Stevens, was barely notable for being the guide to the best places to solicit prostitutes in London. Her mother is Linda Stevens. She attended Ashmole School in Southgate, London.

From a very early age, Stevens was drawn to entertaining people. At the age of five she began taking acting lessons at a drama school near London, but as time went on she seemed to be more interested in fashion than acting. At the age of fifteen her first big break when she beat out 4999 competitors in a modeling competition sponsored by Just 17 Magazine. Following her first modeling jobs Stevens attended the London School of Fashion and after graduation worked in fashion PR, but began to lose interest and started to seek out a career in music instead.

Then, at the age of twenty, Stevens accompanied her brother to an audition in London for a new pop group, which was being put together by Simon Fuller, the one-time manager of the Spice Girls. While waiting for her brother to audition, she was approached by the judges. After many calls and auditions she was chosen as a member of the new band S Club 7, along with Tina Barrett, Paul Cattermole, Jon Lee, Bradley McIntosh, Jo O'Meara, and Hannah Spearritt.

Stevens and "S Club 7" quickly rose to fame, with their debut single "Bring It All Back" reaching number one on the UK Singles Chart in June 1999. The groups follow-up, "S Club Party" was also a hit, the groups self-titled debut album also sold well. The success of their debut album landed the band their own TV show, S Club 7 in Miami. Minor success in the United States followed.

Stevens probably enjoyed more success than the rest of the band members, as she received the most media attention and was a fan favourite. Despite the negative press the male members of the group had been receiving, Stevens was not affected by it and in 2000 was voted the second sexiest woman on the planet by the men's magazine FHM. Around 2002 to 2003, Jo the lead singer had vocal problems for a number of weeks. Rachel took over the role of the lead vocals during this period.

Soon after 2000 the group began to lose steam and they could not live up to past success with both record sales and television ratings down. The group was able to release a successful film in 2003 called S Club Seeing Double but after a UK tour, the members of "S Club 7" commenced to break up.

After "S Club 7" broke up, Stevens signed a £1.5 million solo four-album deal with Polydor Records and re-signed with "S Club 7" manager, Simon Fuller. Breaking out on her own after success with "S Club 7" was hard for Stevens, "I think we ended up conforming to what people's perceptions was," she said about the group. "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." Stevens was the first member from the group to sign a solo recording contract and expectations were high for her first release to be a success.

Her first solo single, written by Cathy Dennis (who has also written for Britney Spears and Kylie Minogue) and produced by Bloodshy & Avant, was "Sweet Dreams My LA Ex", released in September 2003. The single was a hit, debuting at number two on the UK singles chart, beaten to the top spot by the Black Eyed Peas and their international hit single "Where Is The Love?. The single was also a hit worldwide peaking in the top ten in multiple countries including Ireland and Sweden.

Taking inspiration from R&B music most reminiscent of TLC and Sugababes, and adult-style pop music by Madonna, Stevens' debut solo album, Funky Dory was released later that month. The album was a minor hit, reaching number nine on the UK albums chart and quickly fading away in subsequent weeks almost without a trace. Although the album was not a huge commercial success it did gain 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" was released as the second single. The song was hailed as being sophisticated and sexy, like its predecessor, and featured a sample of the David Bowie song "Andy Warhol" from his album Hunky Dory. Hopes were high that the single would be able to match the success of "Sweet Dreams My LA Ex", but like her album the single made a low showing on the charts, peaking at number twenty six and then quickly disappearing. The song was given mixed reviews by pop-critics with some calling 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 choice as a single as it lacked anything special and different, as it did not live up to Stevens' previous single.

In July 2004, Stevens released a brand new single, "Some Girls" which was produced by Richard X. After the commercial failure of both her album and previous single hopes were high for "Some Girls" to perform well on the charts, with critics calling the single her career make or break release. The single became a hit across Europe, and reached number two in the UK. All profits from the single went to the BBC Sport Relief charity. On its release HMV.co.uk called the single Stevens' "finest song to date", and Yahoo! Launch commented "she came to save her career. She ended up saving pop."

Due to 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". On its single release, "More More More" peaked at number three in the UK, giving Stevens her third top ten solo single in the UK. The song was not well received by critics who called the vocals on the song weak and the fact that the song is a cover uninspiring. Stevens herself has stated that she dislikes the song. Nevertheless, the song was a hit and due to the re-release of the album, Funky Dory has sold close to 200,000 copies in the UK to date and was a minor success.

That November, Stevens was nominated for seven awards at the Smash Hits Poll Winners Party. She took home two awards, Most Fanciable Female and Best Dressed Star.

In late 2004, Stevens began working on her second solo album with producers and songwriters Richard X, Alexis Strum and Xenomania. The following March she released the first single from her upcoming album, "Negotiate With Love". The song was a minor hit in the UK, reaching the top ten and received good reviews by critics for its mature and confident sound.

"Negotiate with Love" was followed-up by the song "So Good", which was released in July and was another success when it peaked at number ten in the UK. It was hailed as a good pop song that was "tastily produced and sassily delivered."

The singles were followed by Stevens' second full-length studio album, Come And Get It in October 2005. The album was, like her previous effort, a minor success peaking at number twenty-eight in the UK. Come And Get It sold only 18,000 copies in Britain in its first 3 months, and has been deemed a commercial failure, even though the British pop magazines hailed it as a great pop album. The album was also released as a special 'Limited Edition' CD and DVD, which subsequently became a highly-priced item at online auction sites like Ebay.com

The last single released from the album was "I Said Never Again (But Here We Are)", released in October 2005 the song peaked at number twelve in the UK. The single received some of the best reviews of Stevens' career with it being hailed by HMV.co.uk for its "astonishingly flawless vocal performance" and as Stevens' "most commercially accessible and quirky single since "Some Girls"."

Due to the low charting of the album and its singles no further singles were released, although multiple rumors stated that "Nothing Good About This Goodbye" and the Richard X produced "Crazy Boys" were going to be released as singles. In early January 2006, rumors surfaced that Stevens was to be dropped from Polydor Records. However, a statement was released by the Polydor executives stating that she is still with Polydor.

Just before the release of Come And Get It, Stevens was featured in a documentary, Rachel: My World which was shown on Channel 4's teenage strand T4, with cameras following Stevens around for the summer, at road shows, recording her album, and doing more humble things such as eating out and going to the gym.