Sulfur-rich polymers have attracted many researchers in recent years because of their low cost and broad range of applications. However, direct utilization of elemental sulfur in preparing advanced materials is limited due to its highly brittle nature and low solubility in organic solvents. Inverse vulcanization technique overcomes these issues by reacting sulfur with organic cross-linkers to produce sulfur copolymers. However, these copolymers exhibit much lower mechanical properties compared to the traditional thermoplastics. Thus, in this work, polypropylene-sulfur nano-composites possessing various amounts of sulfur (5 to 30 wt %) were prepared by the solvent-free one-step melt extrusion method, and the effect of sulfur loading on crystallization, mechanical, and thermal properties was investigated in detail. Raman and Fourier transformed infrared spectroscopies indicate the intact structure of polypropylene under extrusion condition. The absence of sulfur peaks in X-ray diffraction and differential scanning calorimetry confirms the homogeneous dispersion. In addition, polypropylene crystalline peaks reduced with respect to sulfur loadings, suggesting the interference of sulfur in the crystallization process. The surface morphology studied by scanning electron microscopy and transmission electron microscopy techniques reveals that the sulfur is completely embedded and uniformly dispersed in the polymer matrix. Rheological behaviors also support the formation of a single phase in the composites. Furthermore, addition of sulfur resulted in significant improvement in the elongation percentage of the polypropylene matrix. The obtained composites are also able to mold into a variety of objects by melt-processing techniques. This work demonstrates the use of sulfur as an efficient solid filler in polypropylene to improve the flexibility and brittleness. The method also provides insights into the new possibilities of sulfur utilization in thermoplastic polymers.