Plasticizers are usually added to improve the mechanical and conditional (thermomechanical) quality of film coatings. Different molecular weights and concentrations of polyethylene glycol were incorporated as plasticizers in hydroxypropylmethylcellulose (HPMC) films. Thermomechanical and mechanical properties of cast films were tested using tensile and dynamic mechanical thermal analysis (DMTA) testing, respectively. The results, as expected, showed that addition of plasticizer caused a decrease in both mechanical and thermomechanical properties, but lower grades had more effect than higher molecular weights and concentrations. The conclusion could be drawn that combining different grades of plasticizers to optimize mechanical and thermomechanical properties is more efficient than using different concentrations of plasticizers.