Hayes signed to the French independent record label, Source Records in 2001, and issued the 4.35am EP and the Work to a Calm EP before releasing her debut album, Night on my Side, in 2002. In 2002 she won Best Female Singer at the Hot Press Awards. The album was nominated for the 2003 Mercury Prize but lost out to Ms. Dynamite's, A Little Deeper. After touring Night on my Side Hayes took two years out from the music industry; "All I do know is that I didn't want to listen to music at all. I stopped listening to the radio. It was like I'd overdosed on music".
In late 2005, Hayes returned with her second album, The Roads Don't Love You, and picked up the Best Irish Female Artist award at the 2006 Meteor Ireland Music Awards, while completing a small tour of Ireland and the United Kingdom. Shortly after this she left Source Records parent company EMI-Virgin as EMI-Virgin was undergoing an overhaul of artists and bands. During this time Hayes co-wrote the song "Hazy" with Adam Duritz.
On August 14, 2006 Hayes announced, via her MySpace profile, that she had begun work on her third album in the Black Box Studios in France, to be produced by her former guitarist, David Odlum. Hayes posted demo versions of a few of the songs on MySpace during recording, including "Out of Our Hands", "Home", and "This Is What You Do".
Gemma Hayes kicking off The Hollow of Morning tour at Cyprus Avenue, Cork City 22 April 2008
Hayes' third album The Hollow of Morning was independently-released on May 2, 2008 in Ireland, and debuted at number 12 in the Irish Albums Chart. Following this she signed a recording contract with the US record label, Second Motion where The Hollow of Morning was released in the US on 30 September 2008. Second Motion works with Daniel Lanois, Adam Franklin of Swervedriver, Brian Vander Ark and others.
Whilst on her 2008 UK tour, Hayes announced that she planned to release an acoustic album by the end of 2008, thought the album has never surfaced. During this time during some promotional work and touring Hayes confirmed that she would start recording her fourth album in August 2008.
In January 2009, it was announced that Hayes had been nominated for Best Irish Female, at the 2009 Meteor Ireland Music Awards, which took place on March 17, 2009 in Dublin. She lost out to Imelda May. On February 13, 2009 she released her new music video for the song "Home" on Myspace; the track was from her 2008 release The Hollow of Morning. On February 19, 2009 she performed at the Oscar Wilde party in Los Angeles, California. The annual event takes place days before the Oscars, and celebrates the best of Irish popular culture.
On February 22, 2009 it was stated on her website that her new EP Oliver will be available for purchase on March 9, 2009. However, it was subsequently announced on Myspace on March 9 that the EP's release had been delayed. A new track called 'Ghost' appeared on Myspace the same day.
On March 13, 2009 Oliver was released on i-Tunes.
On April 14, 2009 it was announced on her Myspace blog  that Hayes began to write new material for the next album.
On September 3, 2009 Gemma performed at the 2012 stage at the 2009 Århus Festival. Her set-list featured new songs Waiting for You and Shock to the System.
On October 20, 2009 Gemma confirmed through her twitter page that she was recording new material in France in the Blackbox studios.
On November 19, 2009 Gemma began a short European tour with performances in Austria, Republic of Ireland, Northern Ireland and the United Kingdom. During these tour dates Gemma played new songs including Tokyo, Waiting for You and Shock to the System. At her gig in Cork on 3 December, Gemma performed a cover of Kate Bush' Cloudbusting.
On December 22, 2009 Gemma released her cover of Kate Bush' Cloudbusting available for free from her website.
In March 2010, Gemma featured on Ceol 2010 a special album in the Irish language. Gemma previously appeared on Ceol 2007. On the Ceol 2010 album Gemma's song Rith me go Crich appeared on the album alongside Bell X1, Kila, The Walls.
Gemma Hayes originally stated on Irish music site Muzu TV that her yet to be titled fourth album would be released in September 2010.[dated info]. However, in October 2010 on Tom Dunne's radio show on Newstalk 106-108, Gemma Hayes said that her new album will not be released until early 2011. In an interview with Irish music website State.ie she confirmed that the album would be released in mid-Spring 2011 either late February or March.
Gemma Hayes has written some original music for the 2010 movie Janie Jones, by writer/director David M. Rosenthal. Abigail Breslin sings and plays her music. The three songs to appear in the film will include Just a Game, Fight for Me and Hurricane.
Gemma Hayes returned to live performances in autumn 2010. She launched her autumn tour in Cork City, Ireland were she performed some new tracks which included Noise, Hurricane and Beside Me.