Prior to joining Connacht, the Belfast High School graduate was with the Ulster Academy for two years before turned professional in 2008. He earned 25 caps for Ulster and has represented Ireland at Schools and A level. McCrea was also a member of the 2008 Churchill Cup winning team, scoring a try against the USA and has three Ireland A caps.
The 6'1, 102kg winger will now link up with Jersey RFC who currently play in the RFU Championship.
Connacht Rugby Team Manager Tim Allnutt said
"We'd like to thank Mark for his dedication and hard work at Connacht over the last two seasons. We wish him all the best with Jersey RFC and with his future rugby career."