Approached by Mark Sharman, then deputy head of sport at Sky, at a Ryder Cup dinner, she began working as a production assistant in 1996, before moving on to the position of editorial assistant on Sky Sports.

She got her presenting break on Sky Sports News in 1998, and since then has been associated with many other sports shows such as 90 Minutes, Soccer Extra, Kirsty and Phil (on BBC Radio 5 Live) and Soccer AM.

Gallacher was nominated for Best Newcomer at the Royal Television Society Television Sports Awards in 1998. She won Satellite/Digital TV Personality at the 2002 Television and Radio Industries Club Awards, and Kirsty’s Home Videos won her the following year’s Satellite/Digital Programme award in 2003. She also won a “Platinum Award” for Best Entertainment Programme at the 2002 Houston International Film Festival.

From 2000 until 2004, Gallacher hosted the Sky1 show Kirsty’s Home Videos, a satellite equivalent of ITV’s You’ve Been Framed! in which viewers send in home videos to be screened. In 2002, she presented the morning show RI:SE, and in 2004 began the show Simply the Best. Gallacher presented the All Star Cup on Sky1 in 2005 and on ITV in 2006. She has made guest appearances on They Think It’s All Over and A Question of Sport. Gallacher presented Ant vs Dec – the popular strand on Ant & Dec’s Saturday Night Takeaway.

In 2005, Gallacher won the third series of the popular Channel 4 reality television series The Games. She then presented the following years alongside Jamie Theakston. In December 2005, she released a DVD entitled Body Sculpt with Kirsty Gallacher in which she shows a variety of workouts. In July 2006, she co-presented the BBC reality TV show Only Fools on Horses.

In 2008, Gallacher presented the new version of Gladiators on Sky1 alongside Ian Wright. She did not return for the second series.

On 30 August 2008, Gallacher appeared on Who Wants to Be a Millionaire? with Duncan Bannatyne.

She has also guest presented GMTV with Lorraine in August 2010 for two weeks and Lorraine on ITV Breakfast.

In May 2011, Gallacher returned to Sky Sports to present for Sky Sports News.

On 27 August 2015, it was confirmed that Gallacher would be taking part in the 2015 series of Strictly Come Dancing. On 5 September 2015, it was announced Gallacher would be paired with professional dancer Brendan Cole for the series. The couple were eliminated on week 6; finishing eleventh.

In May 2018, it was announced Gallacher was leaving Sky Sports.