This time-dependent study aimed to analyze the prevalence of psychological distress in prostate cancer survivors by using claims data in South Korea.In a nationwide cohort, 32 005 patients were identified who were diagnosed with prostate cancer between January 2010 and December 2014. We referred the diagnostic codes of mental disorders as psychological distress. We categorized the prevalence of psychological distress based on age and specific times before and after the cancer diagnosis.The median age at diagnosis of prostate cancer was 70 years. Among 32 005 patients, 3074 (9.6%) were diagnosed at least once with a mental disorder between 1 year before the cancer diagnosis and the last follow-up. Among the first diagnoses of each patient, the common mental disorders were anxiety (39.1%) and depression (33.0%). In the total cohort, there were 54 666 claims for mental disorders and over 48.0% (26 256) were for depression. The frequency of psychological distress peaked just before cancer diagnosis. Anxiety was frequent before diagnosis of prostate cancer, whereas depression was frequent after diagnosis. Although stress reaction/adjustment disorders were relatively high in the younger group, depression was relatively high in the elderly group.Psychological distress in prostate cancer survivors showed different patterns of prevalence between before and after cancer diagnosis, as well as between age groups. Timely diagnosis and intervention for mental health could promote quality of life for prostate cancer survivors.