Microplastics (<5 mm) are persistent emerging contaminants now ubiquitous in all environmental matrices, posing serious ecological and health risks due to their toxic effects, their ability to act as vectors of toxic pollutants and their integration into food webs. Despite extensive global research on freshwater microplastic contamination, only a few rivers in Bangladesh have been studied, with no prior research conducted on rivers inthe Barishal region, which experience increased anthropogenic pressure and have ecological significance. Hence, this research was carried out to provide the first overview of microplastic distribution in the region. A total of 30 surface water samples were collected from ten locations along the length of the river during the pre-monsoon season and analyzed using a microscope and FTIR. The results revealed microplastic abundance ranging from 93.33 ± 8.08 particles/L to 196 ± 11.89 particles/L, with downstream sites exhibiting significantly higher concentrations. Fragments and fibers were the predominant shapes, with red and navy blue as the most common colors. The majority of particles fell under a 100–500 µm size range, followed by smaller particles (<100 µm), indicating a potential for greater pollutant adsorption and bioavailability. Six polymer types were identified: PE (34%), PP (22%), PETE (16%), PS (8%), PVC and nylons (both at 10%). These polymers indicate sources such as municipal waste, industrial discharge, plastic bags, bottles, pipes, packaging materials and fishing nets. Risk assessment through indices revealed an overall moderate pollution scenario where Polymer Hazard Index (PHI) values ranged from 7 to 4236.6 (Category II to IV) and ERI_river=145.86. PLIi and PLI_river values were >1, indicating that all sites were significantly polluted. This study provides baseline microplastic contamination data for the Payra River and is crucial for future research and evidence-based policymaking to ensure sustainable riverine ecosystem management.