Rapid urbanization has resulted in the accumulation of vast quantities of waste rubber (WR) and waste plastics (WP) at the end of their service life. These materials have great resistance to degradation and thus have a longer lifespan. Due to their high resistance to degradation, these materials persist in the environment and pose severe geoenvironmental challenges such as fire hazards, microplastic pollution, and challenges in waste management systems, which adversely impact ecosystems. Therefore, there is an urgent need to utilize the WR and WP to create composites that can be utilized as a manmade resource. Thus, the WR and WP were mechanically shredded to downsize them and thermo-mechanically treated to manufacture polymer composites (pCom). Subsequently, the micro- and macro-mechanical properties (e.g., Young’s Modulus, hardness, tensile strength, flexural strength, impact resistance, etc.) of the pCom were established, and their properties were compared with composites manufactured from virgin materials to evaluate their potential applications. Therefore, this paper aligns with the principles of sustainable development goals by venturing into the transformation of waste materials into resources and addressing the issues of industries and local municipal bodies. The study incorporates samples comprising varying WR-WP ratios and elaborately discusses the changes observed in the performance of pCom. This study highlights the potential applications of pCom to replace conventional polymers supplementing natural resources. Furthermore, the techno-economic, commercial, and environmental advantages of adopting these materials have been emphasized in this study by demonstrating their potential to address industrial and municipal challenges effectively.