Well-preserved leaf macroremains collected in the Bełchatów Lignite Mine (Central Poland) were investigated. Fossil leaves of Acer, Dicotylophyllum, Fagus, Eucommia, Laria, Laurophyllum, Liquidambar, Pinus, Populus, Pterocarya, Quercus, Salix, Salvinia, Taxodium, Ulmus, Vitis, and Zelkova, and fossil fruit of Eucommia were found in fossil assemblage KRAM-P 218 formed in a fluvial sedimentary environment. The fossil assemblage is dominated by plant remains of riparian vegetation of bottomland hardwood forest type. Some taxa point to the presence of mesophytic upland communities. The floristic composition points to warm temperate climate with mild winters, comparable to Cfa type (warm temperate, fully humid with hot summer) in the Köppen-Geiger climate classification. Mean annual temperature of 13.5–16.5°C was reconstructed by the coexistence approach method. Middle to late Miocene age (late Sarmatian to early Pannonian) is suggested for the plant-bearing deposits.