Ulcerative colitis (UC) is a chronic disease of the colon characterized by mucosal damage and relapsing gastrointestinal inflammation. Hydrangea serrata (Thunb.) Ser. and its bioactive compound, hydrangenol, are reported to have anti-inflammatory effects, but few studies have investigated the effects of hydrangenol in colitis. In the present study, we evaluated for the first time the anti-colitic effects and molecular mechanisms of hydrangenol in a dextran sodium sulfate (DSS)-induced mouse colitis model. To investigate the anti-colitic effects of hydrangenol, DSS-induced colitis mice, HT-29 colonic epithelial cells treated with supernatant from LPS-inflamed THP-1 macrophages, and LPS-induced RAW264.7 macrophages were used. In addition, to clarify the molecular mechanisms of this study, quantitative real time-PCR, western blot analysis, TUNEL assay, and annexin V-FITC/PI double staining analysis were conducted. Oral administration of hydrangenol (15 or 30 mg kg-1) significantly alleviated DSS-induced colitis by preventing DAI scores, shortening colon length, and colonic structural damage. F4/80+ macrophage numbers in mesenteric lymph nodes and macrophage infiltration in colonic tissues were significantly suppressed following hydrangenol treatment in DSS-exposed mice. Hydrangenol significantly attenuated DSS-induced destruction of the colonic epithelial cell layer through regulation of pro-caspase-3, occludin, and claudin-1 protein expression. Moreover, hydrangenol ameliorated abnormal tight junction protein expression and apoptosis in HT-29 colonic epithelial cells treated with supernatant from LPS-inflamed THP-1 macrophages. Hydrangenol suppressed the expression of pro-inflammatory mediators, such as iNOS, COX-2, TNF-α, IL-6, and IL-1β through NF-κB, AP-1, and STAT1/3 inactivation in DSS-induced colon tissue and LPS-induced RAW264.7 macrophages. Taken together, our findings suggest that hydrangenol recovers the tight junction proteins and down-regulates the expression of the pro-inflammatory mediators by interfering with the macrophage infiltration in DSS-induced colitis. Our study provides compelling evidence that hydrangenol may be a candidate for inflammatory bowel disease therapy.