The aim of this study was to investigate the diet of Rhinella marina by comparing the availability of food in its environment with its actual diet, and verify whether there is a relationship between the size and volume of its prey and the size of the toad and the width of its mouth. A total of 43 toads (95.55%) presented food items in the stomach. In general, R. marina feeds on the most abundant items in the environment with a niche amplitude of B=0.055. Hymenoptera was the most representative prey numerically. On the other hand, Diplopoda was the most representative prey in volume and frequency. Considering the food importance index (Ix), Diplopoda (Ix=0.47) was the most important part of the diet of R. marina. The relationships between the biometric characteristics of R. marina and its prey are significant with a low coefficient of determination. This result demonstrates that larger individuals predate smaller and lower volume prey, such as ants, and on large prey such as Diplopoda. In general, the diet of R. marina is specialized and is composed of arthropods that occur in greater abundance in nature, but mainly of Diplopoda and Hymenoptera, without selectivity regarding the size of the prey.