Examining the systemic exploitation of mentally ill individuals, this study focuses on the practices of the British colonial administration in Kabba Province, Northern Nigeria (1900–1947). This research investigates how colonial authorities employed biopolitical strategies to categorise, control, and exploit this vulnerable population for labour, prioritising colonial economic and administrative interests. The study utilises a qualitative methodology, primarily analysing archival documents from the National Archives of Nigeria (NAK), Kaduna, and Arewa House Archives (AHA), to uncover the forced labour system’s practices and rationalisations. Crucially, it incorporates oral sources from direct descendants of ethno-medical practitioners, former colonial staff, traditional chiefs, and learned community members. This oral history component provides vital intergenerational knowledge, contextualising archival findings and offering perspectives often absent from official records, ensuring a nuanced understanding of pre-colonial mental health practices and colonial-era lived experiences. Secondary literature on colonial biopower, mental health history, and regional history provides a comparative framework. Findings indicate the colonial administration systematically repurposed traditional care and established new mechanisms to identify, isolate, and compel mentally ill individuals into various forms of forced labour for infrastructure and economic extraction. In conclusion, this research significantly contributes to scholarship on vulnerable populations during colonialism, illuminating the intricate link between mental illness, labour, and power in colonial Nigeria, and informing contemporary debates on mental health, human rights, and historical justice.