Objective: Androgen deprivation therapy (ADT) enhances survival of advanced prostate cancer patients and is therefore used as a concomitant therapy. However, ADT has been reported to cause negative side effects on cognition and emotional processing. So far, research referred to the effects of short-term treatment. Since the brain may adapt to androgen deprivation, we were especially interested in the longterm effects of ADT on cognitive and socioeconomic decision making. Methods: Participants underwent a battery of tests that have been associated with testosterone. We compared the results of three matched test groups: (1) prostate cancer patients with ADT up to 20 years, (2) prostate cancer controls without treatment and (3) healthy controls. We further measured the morning testosterone content in participants' saliva. Results: Testosterone concentration was positively associated with visuospatial performance across and within the test groups. Patients with long-term ADT showed an overall decline in cognitive performance. Compared with untreated patients, ADT was also associated with a reduced intergroup bias during socioeconomic decision making, which was in line with previous observations in young men suggesting that testosterone may promote ingroup favoritism. Finally, depression scores were increased in ADT, while quality of life was negatively associated with the treatment. Conclusion: These findings conform to results made after short-term treatment. ADT promotes negative side effects on cognitive function. We also show for the first time that testosterone deprivation may affect socioeconomic decision making. Nevertheless, it should be emphasized that these effects cannot outweigh the previously described advantages of ADT in the treatment of prostate cancer.