Accumulation of microplastics can significantly impact the food chain in aquatic ecosystems due to their plankton-like shape, which often leads fish and other organisms to ingest them as food mistakenly. Environmental pollution due to microplastics in aquatic ecosystems has long been a concern of researchers. However, few studies have examined the presence of microplastics in Mataram City. This study collected water samples using a bucket and filtered with a plankton net; sediment samples were gathered with a shovel at a depth of 3–10cm (500g); and fish samples were collected from local fishermen. All samples were filtered using a vacuum pump and cellulose filter paper (20µm) and then analyzed under a stereo microscope at 45x magnification. The concentrations of microplastics ranged from 10 ± 5.00 MP/m³-30 ± 22.91 MP/m³ in water, 13.33 ± 23.09 MP/kg-180 ± 173.21 MP/kg in sediment, while in Rastrelliger 0.22 ± 1.04 MP/ind, 0.14 ± 0.38 MP/ind in Sardinella, and 0.11 ± 0.33 MP/ind in Euthynnus with the line containing over 80% of the results. The microplastics varied in size from 250µm to 5mm and were observed in red, blue, black, transparent, and green colors. Through the FTIR analysis, samples showed microplastic particles, particularly PP, PET, PMMA, HDPE, and PE. All sample types found microplastics, indicating significant pollution in the waters of the Ancar River. This study illustrates that the abundance in the Ancar River, Mataram City, is influenced by human activities, environmental conditions, and the characteristics of microplastics.