The present study was aimed to assess the protective effect of aqueous extract of Spinacia oleracea leaves (AESO 250, 500, and 1,000 mg/kg, p.o.) in inflammatory bowel disease using acetic acid- and ethanol-induced colitis in mice and indomethacin-induced enterocolitis in rats. The preliminary phytochemical analysis and further high performance thin layer chromatographic (HPTLC) analysis and phytochemical tests of HPTLC bands confirmed the presence of flavonoids and tannins in AESO. In acute oral toxicity study, administration of AESO (5,000 mg/kg, p.o.) did not show any sign of toxicity and mortality. The treatment with AESO significantly increased body weight, decreased diarrhea with bloody stools, increased blood hemoglobin and plasma total protein, and decreased serum and ileum or colon malondialdehyde content and attenuated the extent of lesions and ameliorated the histological injury of mucosa in all paradigms. The most prominent effects were evident for AESO 1,000 mg/kg. The results of the present study revealed that AESO was effective in attenuating almost all the symptoms of IBD in experimental paradigms. The effect might be due to the antioxidant activity of the flavonoids present in the AESO.