We studied the ecology of Trachylepis atlantica, the easternmost native lizard species in South America, endemic to the Fernando de Noronha archipelago, approximately 350 km off the northeastern coast of Brazil. Activity of this species extended from dawn to dusk, with a peak from 1200–1400 h. Mean body temperature of active T. atlantica was 32.2 ± 2.9°C and was significantly related to both air and substrate temperatures. Trachylepis atlantica used most types of available substrates in the area but was found most frequently (72.5% of observations) on rocks and normally used perches up to 80 cm high. There was sexual dimorphism in body size, with males larger than females. Trachylepis atlantica had an omnivorous diet, with plant material comprising 77% of the volume ingested and being present in 67% of stomachs with food. Formicidae and insect larvae were the main animal items in the diet. Mean prey volume (6.9 ± 5.3 mm³) was small compared to other related species. This, coupled with the high plant consumption, suggests that local availability of suitable prey may be limited, as expected for small islands in general.