Background: Waiting times have been shown to contribute to patient satisfaction with hospital services.Previous studies investigated long waiting times in the hospital, one of which was the time it takes toprepare compounded prescriptions in pharmacy unit. However, few studies have explored the main causesof prolonged waiting times for compounded medications in the hospital. This study aimed to understand thecausal factors that influence prolonged waiting times for compounded prescriptions in Indonesian privatehospital. Methods: A root cause analysis was used to identify the root cause of a reoccurring issue in pharmacyunit. Data were collected from hospital documents, observations, and interviews of 15 representatives fromthe hospital directors, head of pharmacy department, purchasing staff, pharmacy storage manager, otherpharmacy staff, and service quality manager. Results and Discussions: This study identified possible causesof prolonged waiting times for compounded prescriptions which include drug shortage, human resourcesshortage, waiting times for drug preparations, and duration of health insurance coverage confirmation. Inaddition, this study determined the actual causes of the problem, such as managerial, and health insurancefactors which in turn provide suitable recommendations and solutions. Conclusion: It can be concludedthat there were four key factors to the success of hospital pharmacy services: drug and human resourcesmanagement, waiting times for drug preparations, and duration of health insurance coverage confirmation.It is recommended that hospital management could optimize drug formulary management, improvecoordination in drug distribution system to patients, and redesign waiting room in the hospital.