Background: Supervisors should have certain characteristics and adequate preparation for their roles. Yet, there are nowell‑educated experts knowing about the Supervisor’s role and responsibilities and how to train them. So, this research wasconducted with the purpose of finding the factors affecting nursing Supervisor training.Materials and Methods: This research is an inductive content analysis. Participants were 25 in number, consisting of nurses andSupervisors in Shahid Sadoughi University hospitals. The participants were chosen by a purposive sampling method. Data collectionwas done by semi‑structured interviews and reviewing documents. Data were analyzed using conventional content analysis.Results: Findings included two main themes: Firstly, establishment of a Supervisory infrastructure that includes “making theappointments and retention of Supervisors, clarifying the duties and authority of Supervisor, developing Supervisory culture, specializing supervision, and conducting practice‑based training” and secondly, comprehensive Supervisory competencies thatinclude “acquiring scientific, managing, communicative, professional, ethical, pedagogical, and supporting adequacy. ”Conclusions: Clinical Supervisor has a major role in ensuring the quality of nursing care. This leads to improvements in patientcare and nurses’ personal and professional development. So, it is necessary that for effective supervision in nursing, first aninfrastructure is provided for supervision and then the comprehensive competency of a Supervisor is enhanced to apply effective supervision.