Supervised exercise and nutrition programs can mitigate or reverse androgen deprivation therapy (ADT) induced fat mass (FM) gain, lean mass (LM) loss, and impaired physical function. It is unclear whether these benefits are retained following transition to self-management. This study examined the effect of a home-based weight maintenance program on body composition and physical function in obese men with prostate cancer (PCa) on ADT following a 12-week supervised weight loss intervention. Eleven obese PCa patients (74 ± 5 years, 40.0 ± 4.9% body fat) on ADT (>6 months) completed a 12-week self-managed home-based weight maintenance program consisting of 150 min/week of aerobic and resistance training while maintaining a healthy balanced diet. Body composition (DXA), muscle strength (1RM), and cardiorespiratory fitness (400 m walk) were assessed. Significant reductions in weight (−2.8 ± 3.2 kg) and FM (−2.8 ± 2.6 kg), preservation of LM (−0.05 ± 1.6 kg), and improvements in muscle strength and VO2max were achieved across the supervised intervention. Across the home-based program, no significant changes were observed in weight (−0.6 ± 2.8 kg, p = 0.508), FM (0.2 ± 1.4 kg, p = 0.619), LM (−0.8 ± 1.6 kg, p = 0.146), muscle strength (−0.2 to 4.1%, p = 0.086–0.745), or estimated VO2max (0.3 ± 2.1 mL/min/kg, p = 0.649). Self-managed, home-based exercise and nutrition programs are a viable strategy to promote maintenance of body composition and physical function following a supervised intervention in obese PCa patients on ADT.