Breen died on 13 April 2023 after a collision with a post puncturing the cabin of the Hyundai i20 during a pre-event test ahead of the 2023 Croatia Rally.

[1] In 2009, he made the full-time switch to rallying, competing in the Irish, British and International Fiesta Sporting Trophies, winning all three championships.

For his achievements Breen was crowned Young Irish Rally Driver of the Year and received the Billy Coleman Award.

"[10] In 2013, Breen and co-driver Paul Nagle were signed by Peugeot to lead their ERC campaign called 'Peugeot Rally Academy'.

Breen was successful, achieving five podium places during the season, and eventually finishing 3rd overall, missing out on the runner-up spot by only four points.

Midway during the season Nagle left the team to help out Volkswagen's Andreas Mikkelsen in the WRC; from the Rajd Polski onwards, Belgian Lara Vanneste became Breen's co-driver.

[19] Breen moved from M-Sport back to Hyundai Shell Mobis WRT for the 2023 World Rally Championship, again as a part-time driver for the Korean team.

The front left of his car collided with a pole on a road between Stari Golubovec and Lobor at 12:40 pm local time, fatally injuring him.

[25][26] On 17 April 2023, the Fédération Internationale de l'Automobile announced Breen's car number 42 would be retired from the rest of the 2023 season.