He captained the New Zealand under-20s at the 2012 Junior World Championship Heenan was born in Whangārei, and grew up on a farm outside the city with his father and brother, while his mother lived in Auckland.

[1] Heenan has worked as an ambassador with Dóchas don Óige, a community-based training service for troubled youths in Galway on the back of his own experiences growing up.

Heenan signed on a three-year contract for Irish provincial side Connacht in May 2013, joining the team for the 2013–14 season.

[9] Heenan played the full match at openside flanker for Connacht as they produced one of the biggest shocks in the history of the competition, beating four-time champions Toulouse in the pool stages in the Stade Ernest-Wallon.

[13] Heenan returned for the start the 2014–15 season, but suffered a recurrence of his shoulder injury against Newport Gwent Dragons in his first game back ruled him out for five months.

[16] Heenan went on to make 11 appearances in the Pro12 however, including playing the full 80 minutes in the Grand Final as Connacht won the competition for the first time.

Heenan was announced by English Premiership contenders Bristol as having signed for the 2018 season since has played 58 times with 25 points.

Heenan captained the under-20s at the 2012 Junior World Championship, where the team lost to South Africa in the final.