In the present work, ultra-high-molecular-weight polyethylene (UHMWPE) films were irradiated with 130keV He ions. The fluence of the ion beam was ranged from 1x10(12) to 1x10(16)cm(-2). The chemical, morphological, and crystallite structure changes resulted from the ion bombardment were obtained using different spectroscopic techniques. These techniques were Fourier transform infrared spectrometer, scanning electron microscope, X-ray diffraction, and UV-vis spectrophotometry. The surface free energy for untreated and ion-beam-treated samples was determined by means of contact angle measurements of three different liquids. Our results showed a decrease in the crystallinity of UHMWPE and formation of C=O groups on the polymer surface for modified samples as well. A remarkable shifting in the UV-vis spectra toward lower energy and increase in the optical absorption were observed as the ion fluence increases. Measurements of the contact angle indicate remarkable increase in the surface free energy as a function of ion fluence.