The present research work includes non-isothermal crystallization kinetics of poly(ethylene terephthalate) (PET)-titanium dioxide (TiO2) nanocomposites as well as structural and chemical properties of these nanocomposites. The average grain size of chemically synthesized TiO2 nanoparticles has been calculated 19.31 nm by TEM and XRD. The morphology and structural analysis of PET-TiO2 nanocomposites, prepared via solution casting method, has been investigated using SEM and XRD, respectively. The nature of chemical bonds has been discussed on the basis of FTIR spectra. The effect of TiO2 nanoparticles and cooling rates on non-isothermal crystallization kinetics of PET was examined by differential scanning calorimetry at various heating and cooling rates. It has been observed that TiO2 nanoparticles accelerate the heterogeneous nucleation in PET matrix. The crystallization kinetics could be explained through Avrami-Ozawa combined theory. TiO2 nanoparticles cause to make molecular chains of PET easier to crystallize and accelerate the crystallization rates during non-isothermal crystallization process; this conclusion has also been verified by Kissinger model for crystallization activation energy.