Objectives : The purpose of this study is to examine the effects of antioxidant activities and serotonin activities of OnDam-tang-Kami-bang (ODK) on P815 Mast Cell. Methods : The effects of ODK on the activation of DPPH radical-scavenging and SOD in P815 mast cell were investigated. The effect of ODK on the content of serotonin in P815 mast cell was investigated. The effects of ODK on the activation of 5-HTT, TPH-1 mRNA in P815 mast cell were investigated. Results : It was found that the ODK increased SOD activities and DPPH radical-scavenging activities in the P815 mast cell. Also, the ODK decreased the intracellular concentration of serotonin in the P815 mast cell. Further, the ODK decreased 5-HTT and TPH-1 mRNA expression in the P815 mast cell. Conclusions : The results of this experiment reveal that ODK has significant antioxidative effects. However, ODK decreased the intracellular concentration of serotonin and mRNA expression of 5-HTT and TPH-1, which implies that ODK might not be effective for treating depression. Further research exploring the positive aspects of ODK is suggested such that ODK could adequately target symptoms that are to be treated.