While working in galleries, Walsh attended comedy writing evening classes including Stand up and Deliver and as a direct result wrote for Jo Caulfield on BBC Radio 4. In 2006 she switched to comedy full-time. In 2007 Walsh was approached by Frank Skinner to appear in a TV pilot, Frank Skinner’s Skateboarding Dog for Avalon Entertainment.
Walsh was runner-up in AmusedMoose LaughOff 2006 on the Edinburgh Fringe, appeared at the Edinburgh Festival Fringe in 2007 and 2008, and appeared — between writing and filming — at Afterhours as well as co-hosting the AmusedMoose LaughOff 2009 with Jack Whitehall.
Walsh has since written for several TV and radio shows, and has made several appearances on radio and television, including Edinburgh & Beyond on the Paramount Comedy Channel, The Late Edition on BBC Four and Out to Lunch on BBC Radio 2 in 2008.
In 2009, Walsh wrote for and appeared on The Now Show on BBC Radio 4, appeared on Winging It on BBC Switch, and made videos for Current TV. Walsh is also an occasional contributor to comedy podcast Answer Me This! In January 2009, Walsh created a comedy film night called ‘Popcorn Comedy’ with Jon Petrie (brother of CBBC’s Ed Petrie). In the summer of 2009 Walsh was a co-host and writer of Channel 4’s TNT Show.
In August 2011, Walsh was nominated for an Edinburgh Comedy Best Newcomer Award, in recognition of her first full hour-long show. She received critical acclaim for the show which drew on her life since breaking her arm in the Worthing Birdman Competition in August 2010. She has also appeared on “So Wrong It’s Right”, a BBC Radio Four comedy presented by Charlie Brooker.
Walsh also co-wrote Dead Boss with Sharon Horgan, a British sitcom set in Broadmarsh Prison and starring both Sharon Horgan and Jennifer Saunders. The show began airing on BBC3 in June 2012.
She has since made several appearances on popular TV shows, such as The Matt Lucas Awards and Mock the Week.
She has appeared four times on the comedy panel game Just a Minute and won on her debut broadcast on 3 March 2014.