Twelvetrees, who is currently with the England Saxons squad preparing for their fixture against the Irish Wolfhounds on Saturday afternoon will be linking up with his new club team mates when preseason training commences in June.
Twelvetrees himself confirmed that he's looking forward to the future challenge but confirmed his immediate commitment to the Tigers.
"I'm incredibly grateful to everyone at the Tigers for the role they've played in helping me to get to this point in my career and, of course, all the support from the fans I've had over the last three years.
"It's not been an easy decision to make but I am looking forward to joining Gloucester in the summer and being part of what is shaping up to be an incredibly talented young English back line.
"In the meantime though, I'll be fully committed to helping make the rest of the season as successful as possible for Leicester."