PVC, poly(vinyl chloride) is one of the most thermally unstable polymers. Among the large number of supplements required for successful treatment of PVC, significant place have inorganic materials i.e. fillers. Special interests of researchers are nano and microfillers and their influence on the composite properties. In this study, mechanical and thermal properties of poly(vinyl chloride) with different amount of the fillers have been studied. The fillers which were used are natural filler perlite and synthetic filler pyrogenic silica. Glass transition temperature was determined with differential scanning calorimetry (DSC) and thermal stability with thermogravimetric analysis (TGA). Mechanical properties of the PVC polymer matrix and PVC composites were determined on mechanical testing machine by tensile test. To investigate the morphology of the filler particles, distribution of the filler in polymer matrix and the failure mechanism,scanning electron microscope (SEM) was used. Hardness of the PVC and PVC composites were determined using shoremeter A. Results showed that the addition of both fillers did not influence on the PVC glass transition temperature. Analysis of thermal stability has shown that the addition of perlite improves thermal stability of PVC, while aerosil affects PVC's thermal stability only at higher concentration. Analysing the mechanism of failure and mechanical properties, it was concluded that the addition of perlite have negative influence on mechanical properties. In general, the addition of perlite reduces all mechanical characteristic values such as tensile strength, elongation at break and work of break. Aerosil did not affect mechanical properties of the PVC matrix. Addition of both fillers increased the hardness of PVC matrix.