Abstract Foxp3-deficient regulatory T (Treg) cells lack suppressor function and manifest a T effector (Teff) cell-like phenotype. We demonstrate that Foxp3 deficiency dysregulates mTORC2 signaling and gives rise to augmented aerobic glycolysis and oxidative phosphorylation. Mutant Treg cell-specific deletion of the mTORC2 adaptor gene Rictor or expression of a Foxo1 transgene improved regulatory function and ameliorated disease. Rictor deficiency reestablished a subset of Treg cell genetic circuits and suppressed the Teff cell-like metabolic program. Treatment of mutant Treg cells of patients with FOXP3 deficiency with mTOR inhibitors similarly antagonized their Teff cell-like program and restored suppressive function. Thus, regulatory function can be reestablished in Foxp3-deficient Treg cells by targeting their metabolic pathways, providing opportunities to restore tolerance in Treg cell disorders.