The target of rapamycin (TOR) is a crucial intracellular regulator of the immune system. Recent studies have suggested that immunosuppression by TOR inhibition may be mediated by modulating differentiation of both effector and regulatory CD4 T cell subsets. However, it was paradoxically shown that inhibiting TOR signaling has immunostimulatory effects on the generation of long-lived memory CD8 T cells. Beneficial effects of TOR inhibition have also been observed with dendritic cells and hematopoietic stem cells. This immune modulation may contribute to lifespan extension seen in mice with mTOR inhibition. Here, we review recent findings on TOR modulation of innate and adaptive immune responses, and discuss potential applications of regulating TOR to provide longer and healthier immunity.