In April 2019, 25.4 ha of woodland in the Płaska Forest District in the SE part of the Augustów Forest were damaged by fire. Between 2020-2022 a survey of beetles in the burnt and unburnt (control) parts of the forest was carried out. The insects were collected in IBL-2bis window (= flight interception) traps. 781 species classified in 67 families were identified. Among these species, Acrotrichis strandi (Ptiliidae) was found in Poland for the first time, and 41 species were new records for the Masurian Lake District. During the studies, two species protected in Poland (Boros schneideri, Cucujus cinnaberinus), and several more from the Polish Red List of Animals, the Polish Red Book of Animals and the European Red List of Saproxylic Beetles, were recorded. Fifteen of the beetles recorded are relicts of primeval forests in Central Europe: Boros schneideri (Boridae); Stephanopachys linearis (Bostrichidae); Ampedus tristis (Elateridae); Leiestes seminiger (Endomychidae); Platylomalus complanatus, Platysoma deplanatum (Histeridae); Corticaria longicornis, Latridius brevicollis (Latridiidae); Peltis grossa (Peltidae); Stagetus borealis (Ptinidae); Tachyusida gracilis (Staphylinidae); Corticeus fasciatus, C. suturalis, Prionychus melanarius (Tenebrionidae); Colydium filiforme (Zopheridae). The present paper lists the beetles recorded and gives brief characteristics of rare species, primeval forest relicts and a selection of species from the Polish Red List of Animals.