Outsourcing is used as a strategy to improve efficiency, quality, and satisfaction of beneficiaries in hospitals. This study aimed to determine the reasons for outsourcing, outsourced services, achieved objectives, and outsourcing challenges. This qualitative study was conducted through 58 face-to-face semi-structured interviews with chief executive officers (CEOs), chief financial officers (CFOs), and contracting experts (CEs) in 42 public hospitals in Tehran, Iran. Purposive and snowball sampling techniques were used. Interviews were recorded digitally and transcribed verbatim. Data analysis was performed based on an inductive-deductive approach via MAXQDA-10. The Participants included 26 CEOs, 15 CFOs, and 17 CEs. The most important reasons for outsourcing were divided into four main categories including financial resources and funding, customers, management, and factors related to the hospitals. Accessing to up-to-date knowledge and technology, improving service quality and accountability, focusing on strategic points, reducing workload, and increasing patient satisfaction turned out to be the positive outcomes of outsourcing. Weakness in laws and regulations, monitoring and assessment of an outsourced unit, creating dependency and changing organizational culture, as well as human resource issues were introduced as the main pitfalls and challenges of outsourcing. Based on the results, it was suggested that the hospital managers must attempt to outsource services by realistic analysis of the organization's current status. They should specify the reasons and objectives of outsourcing and make decisions based on outsourcing potentials. By taking the current challenges of outsourcing in Iranian hospitals into account, the authorities can make the most efficient decisions with regard to outsourcing.