Abstract Zeolite (ZSM-5 or Y)/polystyrene (PS) composites were obtained by casting evaporation with different proportions (wt/wt) using ethyl acetate as the solvent. The films were characterized by XRD, SEM, water absorption, TG, DSC, and TMA (penetration mode). XRD revealed characteristic peaks of incorporated zeolites. Zeolite microdomains in the polystyrene films were detected by SEM. Water absorption was small, keeping practically constant after 4 h of immersion. TG showed increasing thermal stability of the composites compared to that of the pure PS. DSC revealed no significant changes on glass transition temperatures (Tg). The TMA curves with a 10 mN load showed expansion of composites up to the softening temperature (Ts) and compression of PS film. The Ts data did not show important changes, except for 20 wt% zeolite films. TMA results with a 100 mN load did not present any expansion, but the Ts values were much higher compared to the polystyrene film.