Protein kinase CK2 is a serine/threonine kinase composed of two catalytic subunits (CK2α and/or CK2α′) and two regulatory subunits (CK2β). CK2 promotes cancer progression by activating the NF-κB, PI3K/AKT/mTOR, and JAK/STAT pathways, and also is critical for immune cell development and function. The potential involvement of CK2 in CD8+ T cell function has not been explored. We demonstrate that CK2 protein levels and kinase activity are enhanced upon mouse CD8+ T cell activation. CK2α deficiency results in impaired CD8+ T cell activation and proliferation upon TCR stimulation. Furthermore, CK2α is involved in CD8+ T cell metabolic reprogramming through regulating the AKT/mTOR pathway. Lastly, using a mouse Listeria monocytogenes infection model, we demonstrate that CK2α is required for CD8+ T cell expansion, maintenance, and effector function in both primary and memory immune responses. Collectively, our study implicates CK2α as an important regulator of mouse CD8+ T cell activation, metabolic reprogramming, and differentiation both in vitro and in vivo.