He is known for playing Davey in Hunky Dory, Claude in The Truth About Emanuel, Bobby Willis in Cilla, Tim in Thirteen, King Richard III in The White Queen, William in Dead in a Week or Your Money Back, Gibson in Dunkirk, and Boris Pavlikovsky in The Goldfinch.

[6] Whilst a student at drama school, he appeared in productions of The Caucasian Chalk Circle, Hobson's Choice, The Importance of Being Earnest and West Side Story, in which he played Tony.

[7] He played Melchior, one of the three leads, in the London premiere of the Tony Award-winning musical Spring Awakening, which opened in February 2009 at the Lyric Hammersmith.

[10] He has also appeared in the short TV films The Big Day, Night on the Tiles and the BAFTA Cymru-winning Owl Creek Bridge.

[3] Barnard played the role of Davey and in the film sang songs from the era such as David Bowie's "Life on Mars" and The Who's "Love Reign O'er Me".

[14] He starred as Tim Hobson, boyfriend of Ivy Moxham, (played by Jodie Comer) in the BBC 5 part drama Thirteen.

[16] In January 2023, Barnard starred as Ryan in the Channel 5 series The Catch,[17] alongside Jason Watkins and Poppy Gilbert.