I investigated seasonal predation on arboreal egg masses of four hyperoliid frogs by larvae of ephydrid and phorid flies in the Kibale National Park, Uganda. The egg masses of Hyperolius lateralis, H. cinnamomeoventris, H. platyceps, and H. kivuensis were all vulnerable to dipteran predation. Frequency of predation varied considerably among species, ranging from 61% for H. lateralis to 17.5% for H. kivuensis. Inoculation experiments demonstrated that ephydrid larvae cause high embryonic mortality within a clutch (25–97%) and that fly infestation results in significantly smaller hatching size for surviving tadpoles. Hyperolius reproduction and egg predation rates varied seasonally. Predators were selective during the wet seasons when frog breeding activity was highest, preferentially selecting H. lateralis and H. cinnamomeoventris and avoiding H. kivuensis clutches. Fly predation was random during the dry season. High clutch infestation rates and within-clutch mortality suggest that predation by dipteran larvae plays an important role in determining larval recruitment for arboreal egg-laying hyperoliids at these sites.