The keeper signed a four year contract for the hoops before agreeing to the season long deal with the Championship side.
Doohan travelled with the Celtic first team squad to Austria for pre-season training and appeared as a half time substitute in Scott Brown’s testimonial at the end of last season.
???? | We have a new No. 1… pic.twitter.com/zI3fnbqFwi
— Ayr United (@AyrUnitedFC) July 12, 2018
With Scott Bain competing with Craig Gordon for a first team place, and Connor Hazard as back-up, Brendan Rodgers has the goalkeeping position well covered.
Last season former Celtic keeper Jordan Hart made 25 appearances for Ayr but last night he moved to Queens Park.
After dramatically winning automatic promotion to the Championship on the final day of last season Ayr, who are managed by Ian McCall, opted to go full-time for the new season.
James Forrest’s brother Alan is among the squad at Somerset Park.