Androgen deprivation therapy (ADT) is the mainstay treatment for advanced prostate cancer. By lowering androgen levels, ADT inhibits the progression of prostate cancer, but it may also affect gut autoimmunity. We investigated the association between ADT and the incidence of inflammatory bowel disease using a cohort of 31,842 men newly diagnosed with prostate cancer between 1988 and 2014, identified in the United Kingdom Clinical Practice Research Datalink. Exposure to ADT was treated as a time-varying variable and lagged by 1 year to account for diagnostic delays, with nonuse as the reference category. During 133,018 person-years of follow-up, 48 men were newly diagnosed with ulcerative colitis (incidence rate (IR) = 36/100,000 person-years (PY)) and 12 were diagnosed with Crohn's disease (IR = 9/100,000 PY). In Cox proportional hazards models, ADT was associated with a decreased risk of ulcerative colitis (IR = 24/100,000 PY vs. IR = 50/100,000 PY; hazard ratio = 0.52, 95% confidence interval: 0.28, 0.99) and a nonsignificant decreased risk of Crohn's disease (hazard ratio = 0.38, 95% confidence interval: 0.11, 1.37). These findings indicate that the use of ADT may be associated with intestinal autoimmunity. Further research is warranted to replicate these findings and assess their clinical significance.