To investigate the therapeutic potential of decoy receptor 3 (DcR3) in multiple sclerosis (MS), we used intrathecal (IT) administration of DcR3 into C57/BL6 mice with experimental autoimmune encephalomyelitis (EAE). DcR3 significantly ameliorated EAE symptoms as shown by a lower clinical score and less inflammation in the spinal cord. The expression of TNF-alpha, IFN-gamma, and IL-17 was lower in the spinal cord in IT DcR3-treated mice. Flow cytometry showed a drastic reduction in IL-17-producing CD4 T cells, slightly fewer IFN-gamma producing CD4 T cells and more IL-4-producing CD4 T cells isolated from the central nervous system (CNS) of IT DcR3-treated mice than of controls. Myelin oligodendrocyte glycoprotein (MOG)-specific T cell proliferation was significantly inhibited in DcR3-treated mice. The IL-17 concentration was lower and the IL-4 concentration higher in the supernatants of MOG-stimulated splenocytes from DcR3-treated mice. An adoptive transfer study showed that splenocytes from DcR3-treated mice retained this disease-inhibiting ability. Our data suggest that DcR3 has potential as a suppressor of CNS inflammation in EAE, which may be attributed to either direct inhibition of CNS inflammation or suppression of encephalitogenic Th17 cells. In conclusion, we demonstrate a therapeutic effect of DcR3 in EAE, suggesting its potential for treating human MS.