117 nests of Red-breasted Flycatchers in Białowieża primeval forest (NE Poland) were characterised. Most nests (79%) were built in Hornbeam Carpinus betulus and lime Tilia cordata. Three types of nest sites were distinguished: chimney shaped (26.4%), half cavities (46.4%) or shelves — the nest was wedged under a piece of bark against the main trunk (27.3%). Most cavity entrances were exposed to the south. Compared to other species of secondary cavity nesters in Białowieża National Park, Red-breasted Flycatchers used cavities of a different shape, with a smaller bottom area and at a relatively low height above the ground ( = 4.9 ± 3.13 m). Nesting trees had a smaller diameter ( = 31.2 ± 21.4 cm) and were more often dead (29.8%) than trees used by the other secondary cavity nesters. Only four nest sites were used in consecutive seasons.