A club-record signing from Brighton, Ulloa has adapted seamlessly to life in England's top flight and was on hand to pocket three points after Nigel Pearson's team emerged from a listless first-half performance unscathed at the Britannia Stadium on Saturday.
Peter Crouch spurned a clear 18th-minute chance and rarely allowed the Leicester defence a moment's peace, although further openings were not forthcoming.
Pearson's decision to send on former Argentina midfielder Esteban Cambiasso at half-time proved inspired as the debutant almost immediately settled his new team-mates into the contest.
Ulloa's goal was their reward as Stoke, a fortnight on from their stunning triumph over champions Manchester City, found themselves on the receiving end of a shock result.
The only change to Stoke's victorious XI from the Etihad Stadium was a surprising one as match-winner Mame Biram Diouf dropped to the bench to accommodate Bojan Krkic in attack.
Diouf's lengthy journey back from international duty with Senegal was almost certainly a central factor in manager Mark Hughes' thinking.
Either side of those chances Crouch headed wastefully off target when Leicester inexplicably allowed him a free run at Victor Moses' 18th-minute corner.
Leicester's lacklustre showing prompted a double switch from Pearson, as Cambiasso replaced Andy King and Riyad Mahrez made way for Danny Drinkwater.
The changes lent the visitors renewed impetus but the first chances of the half fell to Moses and Bojan, who hooked over at close quarters and fired into Hamer's chest respectively.
Ulloa, who calmly worked play left earlier in the move, continued his run to apply a back-post finish to Paul Konchesky's low cross.
Hearts were in Leicester mouths three minutes later as Bojan went down under Dean Hammond's challenge in the penalty area, but referee Michael Oliver correctly ruled that the former Barcelona youngster crumpled to ground too readily.
