According to reports emerging out of Italy, the Monegasque was with friends, including his trainer Andrea Ferrari, in the Tuscan city of Viareggio on Easter Monday.
Around 10pm in the evening they were in the unlit Via Salvatori area when Leclerc was recognised by fans and stopped for photographs and autographs.
Amid a mini-scrum, as Leclerc's presence got the attention of more and more fans, a thief managed to snatch Leclerc's watch from his wrist and escaped before he had even noticed.
With the thief having got away, Leclerc reported the matter to the police, who are now investigating and looking into whether the robbery was opportunistic or planned in advance.
Leclerc's trainer Ferrari, who is from Viareggio, made clear his annoyance in a social media post on Tuesday.