He is known for his popular comedy festival shows, including I Heart Bunnings, The Kingswood and I and Shape Up! (formerly known as Let's Zumba!). He has also MC'd the Melbourne International Comedy Festival Roadshow. Breen has also done work as a warm-up act and was an assistant on Adam Hills Tonight.
Breen has appeared seven times on The Little Dum Dum Club. His first appearance was the second-ever episode of the podcast, which was posted on November 3rd, 2010. Breen returned to the show over a year later, appearing with Michael Chamberlin on the 66th episode of the show. It was posted on January 5th, 2012.
Later in 2012, Breen returned alongside Tom Ballard. His most recent apperance came on the show's 145th episode, in which he appeared with Scott Dooley. The episode is one of the show's most notable to date, as it circulates almost entirely around Karl Chandler's "hypothetical" audition for Australia's Got Talent. Breen's next appearance on the show came in episode 166 - which, coincidentally, once again featured Ballard. He then appeared on the show's 191st episode alongside Karl Woodberry. Breen was also a part of the live 200th episode of the podcast in August 2014.