Background: Men affected by prostate cancer who are undergoing hormone therapy can endure a range of symptoms that can adversely affect quality of life. Little research has been conducted to date, to understand the specific unmet supportive care needs of this patient group within the context of current service delivery. Objective: The aim of this study was to understand the experiences of unmet supportive care needs of men affected by prostate cancer on hormone therapy in the United Kingdom. Methods: Mixed methods study recruited 31 men with ≥T3 prostate Cancer or worse and treated by hormone therapy. A small cross-sectional survey (European Organization for Research and Treatment of Cancer [EORTC] C30 and PR25, Self-Management Self-Efficacy Scale, and the Supportive Care Needs Survey) was used to inform the interview schedule. Semi-structured interviews were conducted, and framework approach was used to analyze the data. Results: Complex unmet supportive care needs that were related to physical, psychological/emotional, intimacy/sexual, practical, health system/informational, existential, and patient/clinician communication needs are experienced. Men articulated that current healthcare delivery is failing to provide a holistic person-centered model of care. Conclusion: This is one of the few studies that have identified the unmet supportive care needs of men receiving hormone therapy for ≥T3 prostate Cancer or worse. The needs are multiple and far-ranging. Implications for Practice: Despite national cancer reforms, unmet supportive care needs persist. The findings from this study may be central in the re-design of future services to optimize men's quality of life and satisfaction with care. Clinicians are encouraged to use these finding to help them optimize care delivery and individual quality of life.