Objective(s): Donors contribute to financing, generating resources and providing healthcare services. This study aimed to explore donors' participation in healthcare delivery in health system of Iran Methods: This qualitative study was performed using semi-structured interviews with 36 healthcare donors and 26 policy makers, managers and employees in social affairs deputy of the health ministry and universities of medical sciences in 2018. Purposeful and snowball methods were used for recruiting interviewees. In addition, document analysis was performed using related laws, regulations, policies, plans, etc. Thematic analysis method was used for data analysis. Results: Donors participate in the delivery of physical, mental, and social healthcare services at preventive, curative and rehabilitation levels in Iran. Donors participate in the delivery of healthcare services individually or in groups. They are involved directly through providing healthcare services and indirectly through building healthcare facilities and repairing healthcare technologies and instruments. Conclusion: Donors have significant roles in providing healthcare services in Iran. Hence, policy makers and managers should coordinate and maximize their participation using appropriate donor relationship management (DRM) strategies.