The main objective of this study was to get acquainted with the most important types of nanofillers and their affects on the thermal stability of the polymers, shown in the researches of numerous scientists, based on thermogravimetric results and analysis. Polymer nanocomposites exhibit significantly better properties compared to pure polymer or classical composites thanks to dispersion of nanoparticles fillers. Previous studies have shown that the addition of nanofillers have a mostly positive effect on thermal stability, but may be negative or minor depending on numerous factors such as the amount and way of modification of nanofillers or the atmosphere and temperature range in which the degradation is monitored. The reasons for the positive effect of nanofillers on the thermal properties of the polymer may be: (i) limited thermal movement of polymer chains between the filler layers, (ii) presence of the nanofiller as a barrier to reduce the permeability of volatile degradation products from the material and (iii) a significantly greater part of the matrix in the interphase, thereby leading to improved filler dispersion and strength of interaction at interface polymer/nanofiller. Sometimes there might be a double action of the nanofiller which first acts as a thermal insulator and a barrier to the transfer of volatile products formed during decomposition, but on the other hand, the catalytic action of the clay layers accelerates the degradation of the polymer which ultimately causes a slight or negative effect of nanofiller addition. Remaining impurities, additional components or residual contents of catalyst for the synthesis of nanofiller can also cause a negative effect on the thermal stability of the nanocomposites. Based on the previous studies, the addition of layered nanofillers in comparison to other types of nanofillers contributes mostly to the thermal stability of the polymer.