This paper describes the study conducted to evaluate the antiproliferative activity of ether and ethanol extracts isolated from Piptoporus betulinus against cancer-derived cells. The fungal material used for extract preparation and further experiments was obtained from in vitro grown strains of P. betulinus. To the best of the authors knowledge, this is the first study evaluating antiproliferative potential of in vitro cultured birch polypore fungus. The effect of ether and ethanol extracts on cell proliferation, viability, and adhesion was assessed on colorectal adenocarcinoma cancer cell line LS180, whereas the cytotoxicity effect was investigated in normal colon epithelium-derived cell line CCD 841 CoTr. Studied extracts highly decreased the viability of cancer cells, slightly inhibiting proliferation and tumor cell adhesion in a time- and dose-dependent manner. Cytotoxicity of extracts against cells of normal colon epithelium origin was observed only at the highest studied concentration. The obtained results may seem interesting in comparison with previous studies on water extracts from natural grown P. betulinus. Future research on mycelial extract activity, as well as the content analysis, is needed.