Premier League: Stoke 0 Leicester 1
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.
Stoke captain Ryan Shawcross found himself sporting a bandaged head following a nasty early collision with Jeffrey Schlupp but the sight of his team-mates enjoying the better of the first half went some way towards easing his pain.
An injury sustained by Kasper Schmeichel on international duty with Denmark in midweek meant a Leicester league debut for Ben Hamer and the goalkeeper twice flapped nervously under pressure from Peter Crouch.
Either side of those chances Crouch headed wastefully off target when Leicester inexplicably allowed him a free run at Victor Moses' 18th-minute corner.
The former England striker was rarely out of the action and, after a deserved 29th-minute booking for a reckless lunge on David Nugent, he swivelled brilliantly to volley over from the edge of the area and sent a rasping drive narrowly wide across Hamer.
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.
Nevertheless it was Leicester who broke the deadlock in the 64th minute with a wonderfully worked goal on the counter attack.
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.
The impressive Liam Moore made a vital challenge to deny Jonathan Walters after Crouch brought down a raking ball forward, but, as Stoke mounted a final assault, Shawcross was forced into a similarly last-ditch tackle to thwart Drinkwater.
Leicester only appeared to be truly hanging on when Hamer made brilliant point-blank saves from Diouf and Moses in the final minute of normal time, and if they can grow in stature throughout the season as they did during this game then it should make for a happy Premier League return.