<i>Objective:</i> Vascular abnormalities and expression of proangiogenic factors have been repeatedly reported in inflammatory bowel disease (IBD). Thrombospondin 1 (TSP-1) is a protein well known for its antiangiogenic and anti-inflammatory properties. Using the dextran sulfate sodium (DSS) model, the role of TSP-1 in IBD has been investigated in vivo. <i>Methods:</i> TSP-1-deficient mice (TSP-1^–/–) and WT mice were treated with DSS for 7 days. Disease activity indices, myeloperoxidase activity (MPO) and histology were analyzed. Microvascular density (MVD) was quantified using immunohistochemistry (IMH) with CD31 antibody. TGF-β₁, basic FGF, VEGF, TNF-α and MMPs protein levels were evaluated by IMH and enzyme-linked immunoabsorbent assay (ELISA). Mice were treated with ABT-510 (Abbott Laboratories), an antiangiogenic TSP peptide, using miniosmotic pumps for 7 days. <i>Results:</i> TSP-1^–/– mice had a worse clinical outcome and exhibited severe signs of rectal bleeding compared to the WT controls. The TSP-1^–/– mice showed a higher level of crypt damage and deeper lesions. The grade of inflammation and the levels of MPO activity were also significantly higher in colons of TSP-1^–/– mice. TSP-1^–/– mice displayed higher MVD in focal areas of the colon after only 3 days of DSS treatment. Furthermore, clinical severity of the colitis and angiogenesis was significantly diminished when mice was treated with ABT-510. <i>Conclusions:</i> These findings directly link TSP-1 as a protective factor in IBD and suggest antiangiogenesis treatment, including compounds such as ABT-510 as an adjuvant therapy for IBD.