Thermoplastic composites exhibit improved mechanical performance compared to pure matrices, and the fiber is usually the most influential component of the composite. Recently, studies related to the use of vegetable fibers have grown significantly, but few works report the direct comparative between inorganic and vegetable fibers and fillers as reinforcements. In this work, composites were produced with polystyrene (PS) matrix, reinforced with inorganic fibers (glass), vegetal fibers (kapok), particulate inorganic (CaCO3), and vegetal (wood) fillers. The composites were mixed by a twin‐screw co‐rotating extruder and after processed in an injection‐molding machine. Statistical analyses of density, tensile and flexural strength abrasion resistance were made, along with analyzes of thermal deflection temperature, dynamic mechanical analysis, and scanning electron microscopy were performed on the composites. The main results indicate that all reinforcing agents (vegetal and inorganic fibers and fillers) show a regular trend of increasing the mechanical properties proven by statistical comparison, presenting p < 0.01 that proves a significant increase. By dynamic mechanical analysis, vegetable reinforcements showed a higher coefficient of effectiveness when compared to composites produced with inorganic reinforcements.