Abstract: Fucoxanthin is a natural carotenoid that is isolated from seaweed. We evaluated the effects of fucoxanthin-rich brown algae extract (FX-BAE) on the development of dextran sulfate sodium (DSS)-induced colitis, and colitis-associated colon cancer (CACC) in BALB/c mice. Colitis mice were given drinking water containing 3% DSS for 14 days, and fed with or without FX-BAE (1, 2.5, or 5 g/kg bodyweight/day) from day 8 to day 14. Another way, CACC mice were treated with azoxymethane (AOM) and 2% DSS, and fed with or without FX-BAE at 0.5, 1, or 2.5 g/kg every 2 days. Results revealed the disease activity index (DAI), nitric oxide (NO), malondialdehyde (MDA), tumor necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) were all significantly less in FX-BAE treated mice. Additionally, FX-BAE not only decreased the incidence of colonic neoplasm, but also increased superoxide dismutase (SOD) production, lymphocyte proliferation and survival rate in CACC mice.