We report the first study of diet composition of a Pyrenean lizard of the genus Iberolacerta, the Aurelio's lizard, I. aurelioi, living in an alpine rocky slope at 2300 m of altitude in Andorra. Diet composition was studied during two years from 289 faecal pellets containing 966 prey items. Number of prey per pellet shows annual, seasonal and sexual differences. Diet of the species is poorly diverse, mainly dominated by insects, but we find clear evidences of opportunistic cannibalism based on the presence of toes and scales in feces. In addition, we detected minor sexual, annual and month differences in prey presence and abundance. Low amplitude of trophic niche width and prey diversity, as well as predation on clumped prey and cannibalistic behaviour suggest that Iberolacerta aurelioi has a remarkable dietary strategy in response to strong thermal and food availability constraints at high mountain habitats.