This study was conducted from August to September 2021 and aimed to detect parasites and to determine their prevalence in the digestive tract of mackerel (Scomberomorus commerson) in Belawan, North Sumatra Province. Fish samples were randomly taken from the study site and classified according to length and weight before being dissected at the Laboratory of the Technical Implementation Unit for the Application of Quality of Fishery Products (UPTPMPH), Medan. The mackerel's gastrointestinal system was collected and observed under a microscope to detect the presence of parasites. The result of this study showed that four genera of parasites were identified, which infected the organs of mackerel in the intestines and stomach. The prevalence of Rhadinorhynchus sp. was found to be 40% in the intestine and 6.66% in the stomach. In contrast, Anisakis sp. and Camallanus sp. were only found in the intestine with prevalence rates of 6.66 and 36.66%, respectively. Lecithocladium sp. was found in the stomach with a prevalence rate of 16.66%. Moreover, the highest prevalence was observed in the intestine and stomach for Rhadinorhynchus sp. This parasite often attacks most fish, while Anisakis sp., Camallanus sp., and Lecithocladium sp. were found exclusively in different organs.