Abstract Glycerol channel aquaporin 9 (AQP9) has been reported to be highly expressed in memory CD8 T cells post infection, but its function in memory CD8 T cells formation remains unknown. In this study, we report that AQP9 is vitally required for survival and differentiation of memory T cells after viral infection. AQP9 imports glycerol into cells for fatty acid esterification and triglyceride storage. Loss of AQP9 substantially impaired lipid storage and caused antiviral CD8 T cells sensitive to apoptosis. Interestingly, this defect could be rescued by ectopic expression of glycerol channels or triglyceride synthases. Furthermore, IL-7 induces AQP9 expression dependent on Foxo1 pathway. This study revealed an unexpected role of glycerol in CD8 T cell fate decision by regulating energy storage.