Objectives: This study was carried out to find the effects of Changchuldoin-tanggamibang (hereinafter referred to CDIT) on the inhibition of arthritis induced by collagen on DBA/1J mouse. Methods: The experimental mice were divided into four groups: normal group (Nr), control group (CIA-CT), methotrexate group (CIA-MTX), and Changchuldoin-tanggamibang group (CIA-CDIT). Cytotoxicity, hepatotoxicity, arthritis index, value of immunocytes in draining lymph node and paw joint, and rheumatoid factor (IgG, IgM) in serum were measured in vivo. Results: 1. Cytotoxicity against hFCs was not shown in any concentration. 2. Hepatotoxicity was low in the CDIT-treated group compared with the MTX group. 3. The arthritis index decreased significantly. 4. In total cell counts of DLN and paw joint, the cells in DLN increased significantly while there was a significant decrease in paw joint. 5. In lymph nodes, CD19+, CD3+, CD4+, CD8+, CD3+/CD8+, CD3+/CD69+, CD4+/CD25+, CD3+/CD49b+, and CD4+/CD44+ cells increased significantly, while B220+/CD23+, and CD11c+/MHCII+ cells decreased significantly. 6. In joints, CD3+, CD4+, CD4+/CD25+, and CD11b+/Gr-1+ cells decreased significantly. 7. The level of IgG decreased and the level of IgM significantly decreased compared with the control. 8. Anti-collagen II in serum decreased compared with the control. 9. Around the joint of the CDIT group, infiltration of inflammation, synovial hyperplasia, invasion of cytokine, of cartilage, deposition of collagen and synovial injury decreased compared with the control in histopathologic observation (HE, MT staining). Conclusions: Comparison of the results for this study showed that CDIT had immunomodulatory effects. We expect that CDIT could be used as a effective drug for not only rheumatoid arthritis but also another auto-immune diseases. Therefore, we have to survey continuously, looking for effective substances and mechanisms in the future.