Microplastics (MP) consist of plastic particles ranging in size from 0.02 µm to 200 µm and represent a significant environmental problem. MP originates from primary sources, such as cosmetic products, and secondary sources, including the fragmentation of larger plastics. Due to their non-recyclable nature and resistance to degradation, MP accumulates in the environment, threatening marine organisms and humans through the food chain. A study conducted on golden grey mullet (Chelon auratus Risso, 1810) from the Bay of Medulin, part of the NATURA 2000 ecological network, analyzed the presence of MP in the digestive tracts of these fish. Bay of Medulin is known for its rich biodiversity, and samples were collected during fishing activities from March 2020 to May 2021. The analysis included the digestion of the digestive tract and microscopic identification of MP. In the 31 analyzed specimens of golden grey mullet, a total of 123 MP filaments were detected, with black and blue filaments being the most prevalent. The presence of MP in the digestive tracts of these fish may indicate the burden of plastic waste on the Bay of Medulin ecosystem. Despite challenges in laboratory conditions, the analysis method proved effective in detecting MP. Therefore, the golden grey mullet could serve as an indicator species for monitoring marine plastic pollution.