This study examines language shift among Bahasa Belait speakers in Brunei as a means of adapting to the social challenges of migrating to Brunei. Regarded as one of the minority languages in Brunei (Martin 1995), Bahasa Belait is a non-Malay isolect (Nothofer 1991) of the Baram–Tinjar subgroups of the North Sarawak language (Blust 1972). Martin (1995) reported that Brunei Malay is the first language for Belait people under 35, which indicates that a language shift from Bahasa Belait to Brunei Malay occurred a few decades earlier. This shift, resulting from the speakers’ migration from North Sarawak to Kuala Balai in Belait District, can be traced through the phonological, morphosyntactic, and lexical aspects of the language, which features assimilation of aspects from local languages and dialects. This study explores how the Belait people adapted to their ‘new home’ through assimilation into Brunei culture and engaging in transnationalism with Belait communities back in Sarawak. It uses historical linguistics, interviews with Belait speakers and examination of factors that influence language shift. Culminating in tracing the community’s journey towards being legally recognised as one of the seven Puak Jati (indigenous groups) in Brunei Darussalam.