Nicotinamide adenine dinucleotide (NAD⁺) supplementation attenuates demyelination in the experimental autoimmune encephalomyelitis (EAE) model. The aim of the study was to confirm the therapeutic effect of NAD⁺ on the EAE model and investigate its protective mechanism. Mice were divided into 3 groups: EAE, EAE + NAD⁺, and Control (Ctrl). EAE and EAE + NAD⁺ groups were induced with myelin oligodendrocyte glycoprotein (MOG) to initiate the demyelination process. The EAE + NAD⁺ group received an NAD⁺ injection at a dosage of 250 mg/kg/day. Clinical, neuroinflammation, and neurodemyelination scores were monitored. At the peak of onset, animals were euthanized, and mRNA expression level in the spinal cord was tested. NAD⁺ supplementation promoted the conversion of regulatory T cells (Tregs) into T helper 17 (Th17) cells with increased concentrations of NAD⁺. NAD⁺ alleviated neuroinflammation, attenuated central nervous system (CNS) demyelination, and improved the disease score of EAE mice. NAD⁺ promoted expression of the cytokine interleukin 17A (IL-17A).