Background: Previous anxiety and depression can influence current anxiety and depression, and psychological resilience may be a buffer against current anxiety and depression. However, despite the relevance of these two sets of predictors of anxiety and depression, and their potential in treatment planning, no reports have been published on their role in post-diagnosis anxiety and depression among prostate cancer (PCa) patients. Therefore, this study aimed to determine the roles of these predictors in a sample of men with prostate cancer. Method: Retrospective self-reports of anxiety and depression for how they were before receiving their diagnosis of PCa and at the time of testing after their diagnosis were collected from 425 PCa patients across two states of Australia. In addition, self-reported current psychological resilience was measured. Results: Although there was a significant increase in depression and a nonsignificant increase in anxiety from before their diagnosis, for the whole sample, over 33% of participants reported decreases in anxiety and nearly 21% said that their depression had decreased after diagnosis. Current anxiety and previous anxiety were the strongest predictors of current depression, but resilience significantly moderated those relationships. Participants whose anxiety and depression did not change following diagnosis had significantly higher resilience scores than patients whose anxiety or depression either decreased or increased. Conclusion: Patients' pre-existing anxiety or depression were significant predictors of whether they became depressed following their diagnosis. However, the ability of some patients to cope effectively with their diagnosis suggested potential avenues for peer support for those patients who did not cope with their diagnosis and became depressed. The ''buffering'' role of psychological resilience against depression following major stress is supported by these data.