Microplastics (MPs) are persistent environmental pollutants of growing concern, threatening aquatic ecosystems worldwide. This study examined the influence of different pollution sources on the abundance, types, and polymer composition of MPs in two South African river systems, the uMsunduzi and Swartskop Rivers. Surface water and sediment samples were collected from sites impacted by industrial, wastewater, agricultural, and urban activities. Both rivers showed high MP contamination, with the highest concentrations detected in industrial and agricultural zones. Fibers dominated the particle shapes, while polyethylene (PE) and polypropylene (PP) were the most common polymers, alongside site-specific contaminants such as polytetrafluoroethylene (PTFE). Sediments generally contained higher MP concentrations and smaller particles than surface waters. These findings highlight the role of land use in shaping MP pollution profiles and the need for targeted mitigation strategies to protect freshwater systems.