Multiple sclerosis (MS) and the corresponding animal model, experimental autoimmune encephalomyelitis (EAE), are chronic neuroinflammatory autoimmune diseases. Increased activation of CD4+T cells, especially the Th1 and Th17 subsets, is thought to play a causal role in this disease. IFN-β is widely used in the treatment of MS and is found to decrease IL-17 and OPN production in MS patients and EAE mice. However, a definitive molecular mechanism has not yet been fully elucidated. In this study, we investigated the immunomodulatory effect of IFN-β on the EAE model. We observed disease progression and determined the percentage of Th1/Th17 cells in the peripheral immune organs, brain, and spinal cord of mice. Furthermore, the levels of related cytokines and transcription factors were measured in splenocytes, and the effects of IFN-β on Th17 differentiation were assessed in vitro. Compared to the control group, IFN-β treatment significantly reduced the incidence of EAE and the associated pathological damage. Th1 and Th17 cells in IFN-β-treated mice were significantly reduced, and the levels of cytokines, such as IFN-γ, IL-17, and OPN, were significantly decreased in splenocyte supernatants as well as the levels of corresponding transcription factors. IFN-β inhibited downstream inflammatory cytokines through the inhibition of PI3K/AKT/NF-κB axis and p38, JNK-MAPK, as well as the regulation of mTOR complexes. Moreover, IFN-β inhibited Th17 differentiation and neutralizing OPN antibodies offset the inhibitory effect of IFN-β on Th17 cells. Meanwhile, IFN-β influenced the acetylation of the Il17a and Opn gene promoters. The findings described herein provide novel evidence for the role of IFN-β in Th17 differentiation partly through the inhibition of OPN.