Sea cucumber is a traditional food item in Asia and has been reported to exhibit antifungal, antitumor, and antioxidant bioactivity as well as other properties. In this study, sea cucumbers were treated with hot water at 98°C for 60min to prepare extracts that were then used to assess their effect on the proliferation and H₂O₂ susceptibility of human colon adenocarcinoma Caco-2 cells. The growth of Caco-2 cells was significantly inhibited by sea cucumber extracts in a dose dependent manner. Cell proliferation was inhibited by high molecular weight sea cucumber extract at a concentration of 0.108mg/mL. No growth was observed at 1.04mg/mL of the hot water extract after 96h incubation. Cell damage by sea cucumber extract was evident above 1mg/mL. H₂O₂ showed concentration dependent cytotoxity to Caco-2 cells. In addition, coadministration of sea cucumber extracts intensified the H₂O₂ cytotoxity.