Plastic materials have become a part of nearly every aspect of our everyday life. In this study, microplastic contamination in mussel samples collected from Istanbul shores was analyzed. 10% KOH protocol was used for sample digestion and density separation was applied using NaI solution. After microscopic visual inspection, polymer type was confirmed using ATR FTIR method. Out of the 30 samples analyzed, 22 samples (73.33%) contained microplastics. In the 30 samples analyzed, a total of 60 microplastics were detected. Microplastic pollution levels were calculated as 0.13 particles/gram of mussel tissue and 0.5 particles/individual. The most detected polymer type was polyamide (PA) 38%. Films (43.33%) were the most common shape of microplastic, with 200–1000 µm being the most common size range. The results of this study confirm that microplastic contamination is common in the Bosphorus in Istanbul. Considering the continuously increasing plastic production and contamination levels worldwide, it is believed that the situation can become worse in the upcoming future.