Coprophilous fungus, Panaeolus antillarum rarely recorded in Europe, is reported here for the first time from the Augustów Plane, north-eastern Poland. This thermophilic species was found outdoors in August on horse dung mixed with straw. A chemical analysis did not confirm the presence of the psychoactive alkaloids in collected material. A complete description and illustration of the species based on Polish specimens are presented and notes on its taxonomy, ecology, world distribution and comparison with similar taxa — P. semiovatus var. semiovatus, P. semiovatus var. phalaenarum, and others are also provided.