Background: CAPOX as adjuvant chemotherapy is a standard care option for stage III and high risk stage II colorectal cancer(CRC). And then chemotherapy induced diarrhea (CID) is known as one of the dose-limiting toxicities for CAPOX. Although diverting ileostomy is useful for preventing serious complications of high risk anastomosis, it is well recognized that high ileostomy output is hard to manage. Furthermore, the effect of diverting ileostomy on CID of adjuvant chemotherapy is unclear. In this study, we addressed the clinical impact of diverting ileostomy on the dose intensity of adjuvant chemotherapy for CRC. Methods: Patients who diagnosed with stage III colon cancer and stage II or III rectal cancer after curative surgery and received CAPOX as adjuvant chemotherapy during 2011- 2014 were reviewed retrospectively. We investigated the relationship between diverting ileostomy and dose intensity, toxicities and disease-free survival (DFS). Results: 112 patients (median age 60 years, 52% male, 69% colon cancer, 63% stage III, median follow-up 47 months) were enrolled in this study. Of 112 patients, 100 patients were received chemotherapy without ileostomy (non-ileostomy group: NIG) and 12 patients were received chemotherapy with ileostomy (ileostomy group: IG). 112 Patients received 870 chemotherapy cycles. All treatment related grade 3/4 adverse events were documented in 39% of patients in NIG and 33% of patients in IG (P = 0.77). Grade 3/4 of CID occurred in 8% of patients in NIG and 8% of patients in IG (P = 1). Grade 3/4 of neutropenia were recognized in 21% of patients in NIG and 17% of patients in IG (P = 1). Average relative dose intensity (RDI) in NIG were 75.7% and 85.8% for capecitabine and oxaliplatin, respectively. Average RDI of capecitabine and oxaliplatin in IG were 76.1% and 82.7%, respectively. Significant difference of RDI of capecitabine and oxaliplatin were not shown in comparison between NIG and IG (P = 0.93, P = 0.63). The 3-year DFS rate was 85.0% in NIG and 75.0% in IG. The HR for DFS for NIG compared to IG was 1.709 (95% CI, 0.49 to 5.95; P = 0.40). Conclusions: The presence of diverting ileostomy does not affect RDI of CAPOX as adjuvant chemotherapy.