Natural fibers have been widely used for reinforcing polymers, attributed to their sustainable nature, light weight, biodegradability, and low cost compared with synthetic fibers, for example, carbon or glass fibers. The objective of this research was to promote the use of natural resource blended polypropylene (PP) to reduce greenhouse gas emissions and to explore the potential of using grain by-products, such as coconut shell (CS), as fillers for thermoplastic materials. CS (30 wt %) is embedded in the PP matrix of the composite. Thereafter, CS/PP composites were produced utilizing a hot press compounding machine to produce the specimens and a high-speed mixer set at 3000 rpm for five minutes. The impact of coconut shell content on the mechanical and thermal properties of CS/PP composites was examined. The results show CS/PP composite's tensile strength and tensile modulus improved by 36% and 30%, respectively. In the meantime, the CS/PP composite's flexural strength and flexural modulus increased by 16% and 13%, respectively. At a maximum temperature of 260°C, the CS/PP composite demonstrated thermal stability. Due to the unprocessed particles, the coconut fiber appeared on the surface as homogenous particles. Researchers and industry professionals can use these results to help create new products.