This study investigates the role of L-arginine in modulating T cell metabolism and enhancing their survival and anti-tumor activity. Using high-resolution mass spectrometry, the authors generated dynamic metabolome and proteome profiles of human primary naive T cells following activation. They found that intracellular L-arginine levels decrease after T cell activation, leading to a shift from glycolysis to oxidative phosphorylation. Elevating L-arginine levels in activated T cells induced metabolic changes, including increased survival and the generation of central memory-like cells with enhanced anti-tumor activity in a mouse model. Proteome-wide analysis identified three transcriptional regulators (BAZ1B, PSIP1, and TSN) that sense L-arginine levels and promote T cell survival. These findings highlight the critical role of intracellular L-arginine concentrations in regulating T cell metabolic fitness and survival, which are crucial for anti-tumor responses.This study investigates the role of L-arginine in modulating T cell metabolism and enhancing their survival and anti-tumor activity. Using high-resolution mass spectrometry, the authors generated dynamic metabolome and proteome profiles of human primary naive T cells following activation. They found that intracellular L-arginine levels decrease after T cell activation, leading to a shift from glycolysis to oxidative phosphorylation. Elevating L-arginine levels in activated T cells induced metabolic changes, including increased survival and the generation of central memory-like cells with enhanced anti-tumor activity in a mouse model. Proteome-wide analysis identified three transcriptional regulators (BAZ1B, PSIP1, and TSN) that sense L-arginine levels and promote T cell survival. These findings highlight the critical role of intracellular L-arginine concentrations in regulating T cell metabolic fitness and survival, which are crucial for anti-tumor responses.