Significance Fever is a common symptom of infections and inflammation. We observed CD8 ⁺ T cells exposed to febrile-range temperature during activation, augmented mitochondrial mass, and metabolic activity. An adoptive transfer of these cells into tumor-bearing mice led to enhanced antitumor responses, suggesting that exposure to febrile temperature during activation contributes to the development of robust T cell responses. We identified that mitochondrial translation is integral to the enhanced mitochondrial mass and function of CD8 ⁺ T cells exposed to febrile temperature. Collectively, this research raises the possibility that fever may be beneficial for optimizing metabolic and functional responses in CD8 ⁺ T cells.