Herein, we demonstrated the mechanical properties and morphologies of modified polypropylene (PP) using a combination of glass fibers (GFs) and alpha-nucleating agents (TMP-6 or TMA-3) at different loadings with the aid of a compatibilizing agent during melt compounding and compression molding. The structural characteristics and properties of modified PP composites were analyzed. The results indicated that TMP-6/GF/PP and TMA-3/GF/PP exhibited significantly enhanced mechanical performance as compared to TMP-6/PP, TMA-3/PP, and neat PP. The influence of the type and concentration of alpha-NAs on the morphology and crystallization behavior of PP composites was also studied. Compared with that of the GF/PP composite, the impact strength of TMA-3/GF/PP increased up to 179.4 J m(-1) at 0.2 wt% of TMA-3 with moderate improvements in tensile strength and flexural modulus. Scanning electron microscopy (SEM) revealed that there was good adhesion at the interface between the GFs and PP matrix. This method provided an alternative approach for the design of novel PP composites.