Inflammatory bowel disease (IBD) comprises Crohn’s disease and ulcerative colitis. In patients with IBD, intestinal inflammation and psychological comorbidities affect the quality of life. Evidence for the effectiveness of antipsychotics drugs or psychological therapies in patients with IBD is currently lacking. However, several studies have reported that intranasal oxytocin (OT) administration is effective in individuals with psychological disorders. Therefore, in this study, we evaluated the effects of intranasal OT on psychological disorders, using an IBD mouse model established via dextran sodium sulfate (DSS). Our results showed that intranasal OT improved DSS- induced abnormal stress-related behavior and restored the DSS-induced alterations in nNOS/NO, oxytocin receptor (OTR), pERK/ERK and BDNF expression in the hippocampus. Intranasal OT also ameliorated intestinal inflammation. The activity of the hypothalamic-pituitary-adrenal axis and the sympathetic-adrenal medulla axis were also altered by intranasal OT, without affecting the peripherally-secreted OT. Thus, while intranasal OT administration increased the concentration of OT in the hypothalamus compared to that in the untreated IBD mouse, the OT levels in the serum did not change. Intranasal OT increased the percentages of the M1 and M2 type macrophages and regulatory T (Treg) cells in the IBD mice, in contrast it decreased the M1/M2 ratio and the percentage of NKp46+NK cells in the spleen. We found that the protective effects of intranasal OT administration on impaired stress-coping behavior and intestinal inflammation could be abolished by splenectomy. In conclusion, the present study demonstrates that intranasal OT can ameliorate DSS-induced abnormal stress-related behavior and intestinal inflammation.