In this study, we investigated the effect of talc (magnesium-silicate-monohydrate/3MgO.4SiO2.H2O) nucleating agent (NA) on the thermal and mechanical properties of isotactic-polypropylene (i-PP) at loadings ranging from 0.5 to 5% by weight using the melt compounding method. The results demonstrated that NA/i-PP exhibited significantly improved mechanical performance compared to neat i-PP. In addition, the influence of the concentration of the NA on the melting and crystallization behavior of neat i-PP was also analyzed through DSC curves. The tensile and flexural properties of i-PP enhanced as NA concentration increased. Furthermore, scanning electron microscopy revealed that there is a significant difference in the fracture surface between the NA/i-PP and the i-PP matrix. Consequently, it was determined that the NA (talc) used in this study was a good NA for i-PP, improved the mechanical and thermal properties of the product, affected the crystallization properties and the microstructure, and reduced the mold cycle time. Besides these, the use of various additives between talc and i-PP matrix that can improve interface features are expected to be an alternative approach to the new i-PP design with much higher mechanical and thermal properties.