We studied the diet of the subtropical Lygophis anomalus through the analysis of 444 museum specimens collected along all its geographical range. Analysis of the stomach contents of specimens from all its distribution range indicate that this species feeds primarily on anurans, consuming reptiles like occasional items. Most of stomachs presented only one item, while only 14 snakes (16.87%) presented 2–7 items. Prey total length was 4–34% of the snout—vent length of the snakes. Prior to swallowing, the amphibians were usually oriented and ingested from the anterior portion of the body, but no significant relationship was found between volumes or total length of ingested prey and the direction of ingestion. We did not find sexual dimorphism in head length, and diet composition did not vary between sexes. These results and the absence of a significant relationship between snake and prey size suggests that L. anomalus is an opportunistic species that preys on several environments. Its feeding activity seems to depend more on the season that on the day/night cycle.