The appointment was announced last night, 48 hours after Fallon reached the 100-winner mark for this season - his first ton since he began riding in Britain eight years ago.
The Irishman has often seen controversy - including a six month ban up to March 1995 for violent or improper conduct after a clash with Stuart Webster at Beverley. Last autumn he threatened to return home after stewards imposed a series of bans for whip offences.
Fallon will be retained by Newmarket-based Cecil from the beginning of next season.
"Of the more mature young jockeys he's the most exciting I've seen," Cecil said last night. "I've got a good feeling about it. We've been lucky at Warren Place in that we helped to make Joe Mercer and Steve Cauthen champion jockeys and I'd like to think Pat [Eddery] will do it this year. There's no reason why Kieren shouldn't do the same in the future."