Microplastics are ubiquitous in the aquatic environment. However, a limited number of studies have been conducted on the quantification of accumulated microplastics in benthic sediments of freshwater bodies, which pose threat to the health of benthic communities through food chain contamination. The research aims to quantify, categorize, and determine the distribution pattern of microplastic residues in the benthic sediment along the stretch of an alluvial river (adjacent to public and private establishments such as markets, mosques, universities etc.) on the northern part of Dhaka city. A two-step mechanism made up of size-fractionation and density separation was carried out for microplastic extraction. Extracted microplastics were classified based on size, type and density. The mean abundance was 559.03 ± 10.71 items per 500 g. ANOVA indicated a significant variability with respect to location, size and interaction between the two. Correlating size and microplastic number revealed the presence of a higher number of microplastic in smaller size fractions. Contamination was the highest in the sample beside a market (1311 items) and the lowest beside a university (236 items). Discoveries from this study help to reduce the scarcity of knowledge on microplastic contamination in the context of a freshwater body in the study area.