The Almondvale club had been negotiating with the League of Ireland side for almost a week and have now struck a deal which is thought to include clauses based on appearances and future transfers.
Hoolahan should be available to Paul Lambert for Livingston's Tennent's Scottish Cup tie against Alloa a week tomorrow.
Pat Fenlon, the Shelbourne manager, was disappointed to lose Hoolahan but insisted Livingston were landing one of Ireland's most technically-gifted players.
"He will be a revelation in Scotland," said Fenlon. "He is an old-style player, not blessed with lightning place but someone who has the tricks to get by players. His skills could remind you of guys like Shaun Maloney or Aiden McGeady at Celtic, they are probably the best comparisons I could draw. We will be sad to see him go if everything is tied up but everyone at the club wish him well." | 
>> Terms & Conditions