He could feature in Wanderers’ Sky Bet Championship game at home to Blackburn on Boxing Day, if the club are given international clearance.
Heskey returned to action with Bolton’s Under-21 side in a 3-1 defeat against Reading at Leyland on Monday.
Manager Neil Lennon invited his former Leicester team-mate to train with the Championship club and Bolton said the 36-year-old impressed during his recent trial period.
The free agent was most recently on the books of Australian A-League side Newcastle Jets.
Heskey has previously played for Leicester, Liverpool, Birmingham, Wigan and Aston Villa.
Earlier in the month, Bolton signed another 36-year-old, Eidur Gudjohnsen, on a deal that lasts until the end of the season.