In this article, the effects of chemical treatment (sodium dodecyl sulfate, SDS, and SDS pretreated benzoyl chloride) on the physicomechanical, morphological, and weather tests of calotropis gigantea fiber (CGF) reinforced polypropylene (PP) composites were investigated. The outcomes show that CGFs act as reinforcing fillers enhancing the physicomechanical properties (e.g. tensile strength, tensile modulus, and impact strength, hardness, and water absorption (WA)) of composites. PP/CGF composites with benzoyl chloride after SDS pretreatment indicate better mechanical properties than SDS treated and untreated fiber composites. The interfacial properties were examined by scanning electron microscopy (SEM) and it was performed that the interfacial interaction between PP and CGF was enhanced due to the treatment of fibers, which verified the obtained mechanical properties of the composites. The water absorption test showed that SDS pretreated benzoyl chloride-treated CGF composites exhibited less water absorption than both SDS-treated and untreated composites. Weather tests have shown that SDS pretreated benzoyl chloride-treated composites exhibited less loss of tensile strength and tensile modulus compared to both SDS-treated and untreated composites in terms of their decay time.