A substantial number of studies have been completed with respect to human mobility, linguistic diversity, and social sustainability in the Global North, but very few have been undertaken in relation to the Global South. Mobility, diversity, and sustainability are not recent phenomena, but little, if anything, is understood as regards how human mobility leads to linguistic diversity and social sustainability. This article fills this gap by explaining how the transmigrants of Javanese, Balinese, and Sasak ethnic backgrounds, along with the Bima and Dompu host communities, have established the ethnically and linguistically multi-diverse transmigrant communities of Manggelewa on the Indonesian island of Sumbawa. Data were collected from the participant ethnographic observations of the communities. The main strategies for data collection included taking notes, collecting documents, distributing questionnaires concerning human mobility, sociolinguistic diversity, and social sustainability, interviewing key informants, and recording conversations. Employing qualitative, quantitative, and ethnographic analyses, the study exhibits the community’s dynamic mobility, sociolinguistic diversity, and social sustainability. The study displays how human mobility leads to sociolinguistic diversity and how the diversity is used as a resource for sustaining a better interethnic relationship. The dimensions of mobility, sociolinguistic diversity, and social sustainability are discussed, and the factors that are essential for symbolic social sustainability are statistically attested.