The influence of particle size (0.3 and 5.0 mm) and heating rate (5, 10, and 20 °C min –1 ) on the kinetic parameters of pyrolysis of waste tire was studied by thermogravimetric analysis and mathematical modeling. Kinetic parameters were determined using the Friedman model, the Coats–Redfern model, and the ASTM E1641 standard based on Arrhenius linearization. In the Friedman model, the activation energy was between 40 and 117 kJ mol –1 for a particle size of 0.3 mm and between 23 and 119 kJ mol –1 for a particle size of 5.0 mm. In the Coats–Redfern model, the activation energy is in a range of 46 to 87 kJ mol –1 for a particle size of 0.3 mm and in a range of 43 to 124 kJ mol –1 for a particle size of 5.0 mm. Finally, in the ASTM E1641 standard, the activation energy calculated was between 56 and 60 kJ mol –1 for both particle sizes. This study was performed to obtain kinetic parameters from different mathematical methods, examining how the particle size and heating rate influence them.