Grafting poly(methacrylic acid) (PMA) onto polyethylene (PE) powders using a photoinitiated reaction with UV irradiation was carried out, and the effects of PMA grafting on the thermal and surface properties of PE were characterized. The PE-g-PMA powders obtained were analyzed by FT-IR spectroscopy, zeta size analysis, thermogravimetric analysis, and differential scanning calorimetry. PE-g-PMA films were prepared by melt pressing the powders and then analyzed by scanning electron microscopy and contact angle measurement. The hydrophilicity of the PE-g-PMA films increased on increasing the degree of grafting. The heat of melt crystallization, heat of melting, melt-crystallization temperature, and melting temperature of PE-g-PMA decreased with increase in the degree of grafting. This was attributed to the PMA chains hindering the crystallization of PE.