This article discusses the social formation of peasants-fishermen under peripheral capitalism within the ethnicity and class differentiation of the Minangkabau fishing community in the west coast of Sumatra Island. The research aims to analyze the evidence of social formation in peasant-fishermen situation under the domination of a specific variant of capitalism. Peasant-fishermen in the less developed countries are transformed and subsumed by the capital without being dissolved, albeit their production process now forms an integral part of the capitalist economic system. This research conduct in the village of Tiku Selatan and V Jorong, Tanjung Mutiara Subdistrict, Agam District, West Sumatra Province. This research assesses two fishing villages' household heads using questionnaire surveys and fieldwork through observation, interviews, and secondary data. According to the findings, there are three categories of peasants-fishermen economic and occupational background related to modes of production, ethnicity, and class differentiation.