The purpose of the current study was to examine the viability of conducting a theory-based physical activity (PA) intervention on men with prostate cancer, and the impact of PA on quality of life (QOL). Participants were 31 men, average age of 67 years, with localized or metastatic prostate cancer undergoing androgen deprivation therapy (ADT). Global QOL, fatigue, and PA measures were conducted at baseline and following the 12-week intervention. An additional follow-up testing was conducted 4 months following the intervention (n = 18). Both moderate and strenuous bouts of exercise, as well as functional capacity, increased significantly from pre- to posttest. Both fatigue severity and resting heart rate decreased significantly at posttest. A trend toward improved global QOL was also noted. It was concluded that a 12-week home-based PA intervention may provide health and QOL benefits for prostate cancer patients undergoing ADT. Practitioners are encouraged to promote PA for prostate cancer survivors.