He wrote, performed in and co-directed a pilot for BBC Three called Things Talk. As a director, he won the if.comedy Best Newcomer Award with Tom Basden for Won’t Say Anything in 2007 and again in 2009 with Jonny Sweet for Mostly About Arthur.

His one-man play Stefan Golaszewski Speaks about a Girl He Once Loved was performed at the Edinburgh Festival in 2008. Directed by Phillip Breen, it picked up a host of five-star reviews. This was later performed with another play Stefan Golaszewski Is a Widower at the Bush Theatre in London’s Shepherd’s Bush, again to critical acclaim. The two plays have since been published as The Stefan Golaszewski Plays by The Invisible Dot Ltd.

Golaszewski is a part of comedy sketch group Cowards, which also includes Tim Key, Tom Basden and Lloyd Woolf. They made a TV series for BBC Four and their second Radio 4 series came out in late 2008.

He has written a West End play, Sex with a Stranger, that was staged in early 2012 starring Tovey and Jaime Winstone.

His second sitcom Mum, starring Lesley Manville and Peter Mullan, premiered in 2016. Its second series was screened in 2018. The third and final series began its weekly broadcast on 15 May 2019 and was also offered as a boxset on the BBC iPlayer.