Purpose: Advanced prostate cancer (PC) is associated with substantial psychosocial morbidity. We sought to determine whether mindfulness-based cognitive therapy (MBCT) reduces distress in men with advanced PC. Methods: Men with advanced PC (proven metastatic and/or castration-resistant biochemical progression) were randomly assigned to an 8-week, group-based MBCT intervention delivered by telephone (n = 94) or to minimally enhanced usual care (n = 95). Primary intervention outcomes were psychological distress, cancer-specific distress, and prostate-specific antigen anxiety. Mindfulness skills were assessed as potential mediators of effect. Participants were assessed at baseline and were followed up at 3, 6, and 9 months. Main statistical analyses were conducted on the basis of intention to treat. Results: Fourteen MBCT groups were conducted in the intervention arm. Facilitator adherence ratings were high (> 93%). Using random-effects mixed-regression models, intention-to-treat analyses indicated no significant changes in intervention outcomes or in engagement with mindfulness for men in MBCT compared with those receiving minimally enhanced usual care. Per-protocol analyses also found no differences between arms in outcomes or engagement, with the exception of the mindfulness skill of observing, which increased over time for men in MBCT compared with usual care (P = .032). Conclusion: MBCT in this format was not more effective than minimally enhanced usual care in reducing distress in men with advanced PC. Future intervention research for these men should consider approaches that map more closely to masculinity.