The Balik community is the indigenous population residing in the Nusantara Capital, located in the Sepaku District, North Penajam Paser Regency, East Kalimantan Province. The Balik community has a distinct cultural identity that signifies their identity as members of the Balik ethnic group, one of which is the Balik language. This study investigates the impact of migration on the linguistic and cultural identity of the Balik ethnic group residing in the Nusantara Capital, primarily focusing on the gradual decline of the use of the Balik language and its implications for cultural preservation. It employed a qualitative research approach with a case study design. Data were collected through interviews and participant observation. The analysis of the data involved techniques such as data condensation, data display, and conclusion. The case study findings indicate that the Balik ethnic community tends to be reluctant to use the Balik language in daily communication, both within the household and in the Balik community. Several factors contribute to this phenomenon, including the Balik ethnic community’s preference and greater comfort in using the Indonesian language, a lack of appreciation for the Balik language, and intensive interaction with migrants over a prolonged period. This research highlights the need for the preservation of the Balik language and culture, which is a vital component of Balik cultural identity. The implications of these findings include the necessity for language education programmes in schools, the increased cultural events promoting the use of the Balik language, and awareness campaigns to increase appreciation for regional languages. These practical steps are expected to promote the preservation of the Balik language and cultural identity, while enriching Indonesia’s national cultural diversity amidst the increasing migration and urbanisation in the Nusantara Capital. This study significantly contributes to the social and cultural planning and development in the Nusantara Capital and enriches the academic discourse on migration, cultural identity, and language preservation.