PURPOSE: Rates of surgery remain relevant for localized Crohn's disease despite the evolution of novel therapies. However, the effect of immunosuppressive medication on the perioperative outcome including the extent of the resection is still inconclusive and needs to be evaluated. METHODS: In a single-center study, all patients who received ileocolic resection due to localized Crohn's disease were retrospectively assessed and divided into two groups depending on previous treatment (preoperative medication versus therapy-naive). Outcome parameters included patient characteristics, surgical and histopathological aspects. RESULTS: Two hundred thirty-seven patients were analyzed of whom 192 patients received medical treatment prior to surgery. Preoperative treatment had neither an effect on the length of the resected specimen (29.4 cm versus 27.1 cm, p = 0.27) nor on the postoperative outcome. Only rates of conversion were significantly increased for therapy-naive patients compared to patients receiving preoperative treatment (15.6% versus 5.7%, p = 0.025). CONCLUSION: Preoperative medical treatment does not have an effect on the extent of the resected bowel segment in patients suffering from localized Crohn's disease.