We analyzed the stomach contents of 170 specimens of the colubrid snake Mastigodryas boddaerti collected in the Brazilian Amazon. The Boddaert's Tropical Racer feeds primarily on lizards (N = 57; 74.0%), followed by mammals (N = 11; 14.3%), anurans (N = 5; 6.5%), birds (N = 2; 2.6%), and reptile eggs (N = 2; 2.6%). A significant relationship was found between both snout-vent length and head length of the snakes and prey total length, as well as between snake head width and the width of the prey, and between the weight of snakes and their prey, indicating a tendency for larger snakes to capture larger prey. Differences in the diet were observed between sexes, with females feeding on wider prey and males feeding on larger ones (in terms of body length), which may be related to the longer heads of the males relative to females head. No variation was found between adults and juveniles in the relative size of the prey ingested, although a difference was found in the composition of items, with the adults being more generalist than the juveniles. Twenty-seven of the 61 mature females examined had well-developed follicles and three were pregnant. Prey were found in the digestive tracts of 19 (63.3%) of these breeding females, indicating that they continue to feed during the reproductive period. Our study includes unpublished data on the feeding biology of Mastigodryas boddaerti, increasing the knowledge about the species and contributing to a greater understanding of the ecology of tropical snakes.