Background <p>The World Health Organization’s Mental Health Gap Action Programme (mhGAP) intervention guide (IG) offers evidence-based recommendations and instruments for evaluating and comprehensive care of priority disorders. Its objective is to close the mental health gap; yet, this gap remains, characterized by substantial differences in access to and quality of care. Family physicians are essential in bridging this gap; nevertheless, their awareness and engagement in executing mhGAP remain ambiguous. This study explored family physicians’ awareness and involvement levels in the implementation of mental health services in Nigeria as well as the perceived facilitators and barriers affecting their participation in the “Mental Health Gap Action Programme”.</p> Methods <p>This study employed a descriptive participatory action research design, utilizing semi-structured key informant interviews with 24&#xa0;family physicians nationwide, representing all six geopolitical zones. Interviews were transcribed verbatim and analysed using inductive coding and content analysis, revealing key themes and patterns that informed the study’s findings, which were represented thematically.&#xa0;</p> Results <p>Family physicians demonstrated varying awareness of mental health guidelines and interventions. Involvement levels ranged from minimal to proactive as there was no national unified guide. Facilitators to mhGAP involvement and implementation included training of physicians, patient relationships, and multidisciplinary collaboration while barriers included time constraints, stigma, and systemic gaps.</p> Conclusions <p>This study reveals the varying levels of mhGAP awareness and involvement among Nigerian family physicians. While some are proactive, many show limited engagement. Training, patient relationships, and collaboration facilitate involvement, while time constraints, stigma, and systemic gaps hinder it. Targeted interventions are needed to bridge the mental health action gap.</p>