BACKGROUND: In Crohn's disease, postoperative endoscopic activity of small bowel lesions outside the scope of ileocolonoscopy has been insufficiently studied. AIMS: We aimed to assess this postoperative activity using capsule endoscopy (CE) and analyze the association between treatment optimization based on CE findings and the long-term course. METHODS: In patients who underwent intestinal resection, we performed CE and assessed the endoscopic activity using the Lewis score within 3 months postoperatively (1st CE) and during follow-up. Postoperative treatments were adjusted according to clinical symptoms or CE findings (severity of 1st CE or worsening of follow-up CEs). Hospitalization, repeat surgery, or endoscopic dilation defined the primary outcome. RESULTS: Among the CE group (N = 48), 85.7% (1st CE) and 79.2% (2nd CE) exhibited endoscopic activities indicating residual or recurrent lesions. Postoperative treatments were adjusted according to clinical symptoms in the non-CE group (N = 57) and clinical symptoms or CE findings in the CE group. Compared to the non-CE group, the CE group had significantly fewer primary outcomes. Patients with treatment adjustments based on CE findings had even lower primary outcome rate. Multivariate analysis identified the CE group as an independent protective factor (hazard ratio = 0.45, 95% confidence interval = 0.20-0.96). Treatment adjustments based on CE findings showed a stronger protective effect (0.30, 0.10-0.75). CONCLUSIONS: Postoperative repeated CE enabled us to assess residual and recurrent lesions accurately before clinical symptoms appeared. The regular assessment of endoscopic activity and subsequent treatment optimization have the potential for improving postoperative course.