A rare fungus Tricholomopsis decora, included in the Polish Red List of Macromycetes under the category R (rare), has been recorded in the area of the Trójmiejski Landscape Park near Gdańsk, northern Poland. The species occurs in Poland mainly in mountainous areas. It is known from only three lowland localities. The author describes the fungus’ habitat in one of them, the Lasy Oliwskie forests.