The Fuscous Flycatcher (Cnemotriccus fuscatus) is a medium-sized Tyrannidae widespread in South America. Despite its large distribution, there have been very few studies on its diet, especially in different habitats. This study presents data on diet variation in three habitats in the Pantanal wetlands in the state of Mato Grosso, Brazil. The specimens were captured through a mist-netting programme between February 2000 and May 2010, in the Retiro Novo Farm, in the Poconé municipality. Birds were captured in three vegetation types: Landizal, Cambarazal and Cordilheira. Tartar emetic was used to obtain the regurgitation samples identified at order level. We captured 61 individuals (21, 26 and 14 in the above described habitats, respectively). Diet of C. fuscatus differed between the three habitats. Ants and beetles were the most relevant prey items either in numerical frequency (NF) or in frequency of occurrence (OF), in terms of the overall diet (NF = 27.34% and 37.89%; OF = 36.06% and 75.4%, respectively). However, in Cordilheira, seeds and beetles dominated the NF (21.8% and 38.1%, respectively) and OF (28.5% and 85.7%, respectively). Cnemotriccus fuscatus was found to have an omnivorous diet, although in Cambarazal, individuals preyed exclusively on arthropods. The present study provides an important contribution to the knowledge of the diet of a poorly studied Neotropical bird.