A stack of five polycarbonate foils, each 1.4 μm thick, was irradiated with 1.3 MeV 4He+ ions to the dose of 1.1 × 1014 cm−2. Ion beam induced polymer degradation, as a function of the particle energy, was studied by UV-VIS and IR spectroscopy of individual foils. In the irradiated foils, a significant reduction of characteristic absorption bands is observed, indicating polymer degradation. Significant increase of the surface polarity, characterized by a polar component of the surface free energy, is also found. Both the degree of the polymer degradation and the surface polarity correlate with the total energy deposited by 4He+ ions in the foils.