Abstract The NF-κB family of transcription factors plays a pivotal role in T cell activation and survival during (auto) immune responses. IκB kinase 2/β (IKK2) is part of the IκB kinase complex, a central component of the intracellular signaling pathway mediating NF-κB activation. We studied the role of IKK2 in autoantigen-specific T cell activation and induction of autoimmune disease using mice that lack this kinase specifically in T cells (IKK2ΔT cell mice). We found highly impaired myelin-oligodendrocyte-glycoprotein (MOG)35–55-specific T cell activation in vitro and complete resistance to MOG35–55-induced experimental autoimmune encephalomyelitis (EAE) in IKK2ΔT cell C57BL/6 mice in vivo. By contrast, transgenic expression of a pathogenic MOG35–55-specific TCR (2D2 TCR) rendered IKK2ΔT cell mice susceptible to MOG35–55-induced EAE and restored in vitro MOG35–55-specific T cell responses, indicating an expansion defect in IKK2-deficient T cells. Treatment with the IKK2-inhibitory compound PS-1145 reduced MOG35–55-specific proliferation and cytokine production of 2D2 transgenic spleen cells in vitro and diminished clinical signs of EAE in vivo. Our data underscore the potential of therapeutic IKK inhibition in autoimmune diseases.