This study presents a groundbreaking exploration of the nexus between responsible leadership and moral voice in Vietnam’s public health organisations, a context that has been underexplored in the existing literature. It specifically examines the mediating roles of basic need satisfaction and public service motivation as the moderating role of public service motivation. This research is significant as it addresses the gap in understanding how responsible leadership influences moral voice through these mediating and moderating mechanisms. Utilising Self-Determination Theory, and Structural Equation Modelling on data from 429 nurses who work in public hospitals in Ho Chi Minh City and Tien Giang Province, Vietnam, using a convenience sampling technique, the study reveals that responsible leadership significantly impacts moral voice, with basic need satisfaction and public service motivation serving as partial mediators. Notably, this research pioneers in investigating the sequential mediating effects of basic need satisfaction and public service motivation, as well as the moderating effect of public service motivation in the responsible leadership-moral voice link. The work’s contribution lies in its comprehensive examination of the interplay of basic need satisfaction and public service motivation in the relationship between responsible leadership and moral voice within the public hospitals in Vietnam. This provides both theoretical advancement in leadership studies and practical insights for enhancing ethical behaviour and moral courage in public health organisations.