This study aimed to evaluate the relationship between high-output stomas (HOSs), postoperative ileus (POI), and readmission after rectal cancer surgery with diverting ileostomy. Methods: We included 302 patients with rectal cancer who underwent restorative resection with diverting ileostomy between January 2011 and December 2015. HOSs were defined as stomas with ≥2000 mL/day output. We analyzed predictive factors for readmission of these patients. Results: Forty-eight (15.9%) patients had HOSs during the hospital stay, and 41 (13.6%) patients experienced POI. HOSs were strongly associated with POI (45.8 vs. 7.5%, p<0.001). The all-cause readmission rate was 16.9%, with 19 (6.3%) and 20 (6.6%) patients experiencing ileus and acute kidney injury, respectively. HOSs (27.1 vs. 15.0%, p=0.040) and POI (34.1 vs. 14.2%, p=0.002) were associated with all-cause readmission, and POI was associated with readmission with ileus (17.1 vs. 4.6%, p=0.007). POI was an independent risk factor for all-cause readmission (adjusted odds ratio [OR]=2.640; 95% confidence interval [CI] 1.162-6.001; p=0.020) and readmission with ileus (adjusted OR=3.869; 95% CI 1.387-10.792; p=0.010). Conclusions: POI was associated with readmission, particularly for subsequent ileus, in patients with diverting ileostomy. We should make efforts to reduce POI, such as strong control of HOSs, to prevent readmission.