Abstract Background The motivation of health workers is a key concern of policy makers, practitioners and researchers. Public Service Motivation (PSM), defined as the altruistic desire to serve the common interest, to serve others and to help patients and their families regardless of financial or external rewards, has been shown to be key to the performance of public servants. Yet, limited attention has been paid to this kind of motivation in health care settings in low- and middle-income countries. Little is known about PSM and its contextual specificity in the Moroccan health system. We set out to qualitatively explore the meaning of PSM and its expression among health workers in four public hospitals. Methods We adopted a multiple embedded case study design to explore PSM in two well-performing and two poor-performing hospitals. We carried out 68 individual interviews, eight focus group discussions and 11 group discussions with different cadres (doctors, administrators and nurses). We carried out thematic analysis using NVivo 10. Results Our analysis shows that public service motivation is a notion that seems natural to the health workers we interviewed. Daily interactions with patients catalysed health providersâ affective motives (compassion and self- sacrifice), a central element of PSM. It also provided them with job satisfaction aligned with their intrinsic motivation. Managers and administrative personnel express other PSM components: attraction to public policy making and commitment to public values. A striking result is that health workers expressed strong religious beliefs about expected rewards from God when properly serving patients. Conclusion This study highlights the presence of PSM as a driver of motivation among health workers in four Moroccon hospitals, and the prominence of intrinsic motivation and compassion in the motivation of frontline health workers. Religious beliefs were found to shape the expression of PSM in Morocco.