The birch polypore Piptoporus betulinus was among two mushrooms that were found in the Iceman's bag. Recent studies indicated that P. betulinus was probably used as a religious and medicinal item. In order to examine the medicinal potential of P. betulinus, hot water (HW), partially purified (PP), and alkali extract (HA) were prepared and tested for antioxidant, antimicrobial, cytotoxic, and angiotensin I-converting enzyme (ACE) inhibitory activity. All tested samples exhibited moderate cytotoxic activity, and HW appeared as the most effective (IC50 = 0.8 ± 0.1 mg/ml for HeLa cells). HA proved to be a good 1,1-diphenyl-2-picrylhydrazyl radical scavenger and exhibited the strongest ferric-reducing power (EC50 = 0.07 ± 0.3 mg/ml). The same extract (HA) also expressed the strongest ferric-reducing power (EC50 = 0.99 ± 0.1 mg/ml). Hot alkali extraction contributed significantly to ACE inhibitory activity (EC50 = 0.06 ± 0.00 mg/ml) and to antimicrobial activity, especially against highly resistant Enterococcus faecalis (minimum inhibitory concentration: 0.156 ± 0.000 mg/ml; and minimum bactericidal concentration: 1.25 ± 0.00 mg/ml).