In border areas, multi-ethnic communities may experience both positive and negative impacts of being in a border area. On the one hand, being in a border area has a unique beneficial effect since traveling overseas is now easy and affordable. People move across the borders. However, on the other hand, there can be negative impacts because they are prone to conflicts due to several factors, such as differences in language, culture, social aspects, politics as well as economic differences. In this context, the language identity of multiethnic communities in the Kalimantan-Sarawak border area in Indonesia can be seen in the language situation and the factors that influence it. This research examines this issue. The study uses a qualitative method. Data collection employs surveys, observations, interviews and focus group discussions. As techniques. The findings demonstrate that: multi-ethnic communities in border areas are often bilingual. They have the abilities to speak languages other than their own ethnic language; they also exhibit flexibility in cross-language interactions; and the linguistic situation in border areas, particularly regional languages is preserved in families, homogeneous environments, traditional ceremonies, and religious activities. A linguistic identity is characterized by a strong sense of ethnicity: ethnic culture, regional geography, social groups, family and surroundings, regional history, education, as well as economic activities. These are aspects that influence the linguistic identity of the multiethnic population in the West Kalimantan-Sarawak border region in Indonesia.