Casciaro, who works as a policeman in Gibraltar, ran onto a throughball and drilled a low finish through the legs of David Marshall and into the bottom left corner.
The goal came two minutes after Shaun Maloney had given Scotland the lead from the penalty spot.
Prior to Sunday's meeting at Hampden Park, Gibraltar had lost all four of their previous competitive fixtures, conceding 21 goals and failing to score in the process.
But that barren spell was broken by Casciaro, sparking scenes of jubilation among the Gibraltar fans inside the stadium.
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