Microplastic pollution is a significant global environmental concern affecting marine ecosystems and human health. This study investigated the presence and abundance of microplastics in the waters and green mussels (Perna viridis) of the Kalirejo coastal area in East Java, Indonesia, a region known for extensive mussel cultivation. The results showed that microplastics were present in all water and mussel samples, with higher concentrations at shallower depths. Fragments were the most prevalent microplastic type, followed by fibers and films, with polyethylene (PE) identified as the dominant polymer. A strong positive correlation between microplastic concentrations in water and mussel tissues indicates direct environmental uptake. These findings highlight widespread microplastic contamination in the Kalirejo coastal area, raising concerns about environmental impacts and health hazards associated with consuming contaminated shellfish.