In the last two decades, the invasion of the Amur sleeper (Perccottus glenii Dybowski, 1877) originating from the Far East can be observed in Eastern and Central Europe. Since the Amur sleeper is a non‐game fish species, few detailed studies exist on its feeding ecology both in its native and invaded habitats. We examined the seasonal feeding ecology of Amur sleeper in a lentic and in a lotic habitat. Chironomid larvae, zygpoteran larvae, crustaceans, and ephemeropteran larvae dominated the diet. No clear differences between the two habitats were found. The diet composition was mainly regulated by the body size that had stronger effect than the habitat and the season. Although fish consumption was uncommon, we anticipate this finding to the structure of the examined populations, in which large bodied individuals were rare. Our study shows that the Amur sleeper may influence several levels (compartments) of the aquatic food web, although the species proved to be an especially important predator of the invertebrate assemblage.