Venn took a variety of roles as a jobbing actor, using the surname Venice. He got his big break in 2003 when he was cast as Curtis Alexander in the footballing drama Dream Team on the satellite channel Sky One. Initially only contracted to appear in two episodes, he became part of the regular cast, appearing in 98 episodes in all until the character was killed off in 2005.

In late 2006, Venn landed a role in the horror film sequel Return to House on Haunted Hill as Warren, he also had a role in ‘Wrong Turn 3: Left for Dead’ as Walter and a small role in Bourne Ultimatum, as Agent Hammond, and The Dark Knight, as bodyguards of one of the film’s main villains, Gambol. He can also be seen in the music video “Twisted” by Fredi Kruga. Venn guest starred in an episode of the series Little Miss Jocelyn, which aired in January 2008. Venn was also seen on an episode in the third season of Kathy Griffin: My Life on the D-List where Kathy visits the UK and the pair go on a date. His on-screen time lasted just over a minute, and he was subtitled throughout when the episode aired 17 July 2007. Prior to the Hull City-Tottenham Hotspur game on Setanta Sports on 23 February, Venn performed a strange monologue.

He appeared in the play The Brothers by Angie Le Mar at the Hackney Empire for several short runs from 2005. It was televised by MTV Base in March 2009 with Venn, MC Harvey and Jason Barrett in the line-up.

Venn joined the cast of BBC One soap EastEnders in the role of Ray Dixon, the father of Morgan Jackson-King, in November 2011, appearing in the series from 10 January 2012. He departed the show on 28 May 2013. He played a firefighter on the Miranda 2014 Christmas Special: I Do, But to Who?.

On 18 July 2015, Venn made his debut on BBC One’s medical drama Casualty as the new nurse Jacob Masters. He later became a series regular.

In January 2018, Venn participated in And They’re Off! in aid of Sport Relief.

On 21 August 2018, Venn was announced as the fourteenth celebrity to join the Strictly Come Dancing line up of 2018. He was partnered with professional dancer Karen Clifton and they finished in 6th place.