Previous studies have shown that diet varies among seasons and age classes of lizard species inhabiting contrasting environments. The purpose of our study was to compare feeding habits between seasons (wet and dry), sexes (males and females), and age classes (juvenile and adult) of the arboreal lizard Anolis nebulosus from two different environments: a Pacific island (San Pancho Island) and the mainland Pacific Coast (Biological Field Station Chamela) of Mexico. Anolis nebulosus from island and mainland were generalist insectivores. During the dry season, the prey number consumed by lizards from island was lower than for lizards from mainland. With respect to numerical and volumetric data of prey items consumed by females and males for both age classes (adults and juveniles) in both populations (island and mainland), adult beetles, ants, orthopterans (grasshopper and crickets), and spiders were most frequently preyed upon. These results suggest that there are no ontogenetic changes in the diet of A. nebulosus and there is high dietary overlap of all groups (sexes and age classes) within both populations. Selection of this kind of prey by lizards from both age classes may be an overall trend in most species of Anolis, an opportunistic behavior toward the most abundant prey types that occur among seasons and years.