The abundance of microplastic (particles <5 mm) and its danger in marine ecosystems has been reported in numerous studies. This work aimed to quantify microplastic accumulation in seawater, sediment and commercial fish of Dumai waters. Purposive sampling was performed to collect sample, enabling to gain a variety of microplastics and carried out on 5 sampling stations along the coast. Surface water sample was collected using plankton net (mesh size of 0.4 mm), the sediment was collected using a sampling tube (4 inch in diameter) at depth of 0 – 10 cm, and the fish sample was obtained from local fish-landing site of Dumai Port. This study revealed that the microplastics in water and sediment of Dumai waters, reaching up to 61.80-102 particles/m³ and 72 particles/100 g, respectively. Three items of microplastic were identified, namely fiber, the highest (81.9%), filament at 13.9% and fragment was at 4.2%. Microplastic particles were existed in digestive tract of 12 commercial fish samples caught from Dumai waters. The highest level of microplastic pollution was attributed to pelagic fish Atropus atropos (10.3 particles/individual) and the lowest level was found in Setipinna breniceps (3 particles/individual).