This study examines the role of Hindu-Buddhist cultural acculturation in the formation of the cultural identity of the city of Medan. Using a descriptive-historical qualitative approach, data was obtained through field observations, in-depth interviews with traditional and cultural figures, and documentation studies of artifacts and historical sources. The results of the study show that Hindu-Buddhist culture left a strong imprint in the form of archaeological artifacts, traditional symbols, social structures, cosmology, and the art and architecture of the Karo and Malay Deli communities. The process of cultural acculturation is integrative, where Hindu-Buddhist elements do not replace local culture, but are absorbed, reinterpreted, and merged into the value system of the local community. This finding confirms that Hindu-Buddhist culture is an early historical layer that contributes significantly to the formation of the cultural identity of the city of Medan to the present day.