<p>The accumulation of microplastics in sediments of lentic systems facilitates their ingestion by shrimps, raising ecological concerns. This study investigated the correlations between the average amount of microplastics in sediments, gills, and stomachs of <i>Macrobrachium amazonicum</i> (Heller, 1862) in a tropical reservoir in Brazil. Monthly samples and physical and chemical water variables (temperature, conductivity, pH, and dissolved oxygen) were collected. Standardized protocols ensured accurate microplastic identification and minimized contamination. Microplastics were identified in 90.9% of samples. Concentrations were significantly higher in the sediment and gills than in the stomachs, with no difference between sediment and gills. Temporal variation occurred in the gills and stomachs: Gill concentrations peaked in February and were lowest in November–December, while stomach concentrations were highest in September–October and lowest in November–December. Sediment concentrations remained relatively stable over time. Positive correlations were found among all compartments, especially between stomachs and sediment. Generalized linear models showed that dissolved oxygen positively influenced microplastic abundance in both gills and stomachs, while conductivity was also significant for stomachs. The findings reveal the dynamics of microplastics in tropical lentic systems, emphasize the risks of bioaccumulation and ecological effects, and support the implementation of effective management strategies.</p>