TIM‐3 is a molecule selectively expressed on a subset of murine IFN‐γ‐secreting T helper 1 (Th1) cells but not Th2 cells, and regulates Th1 immunity and tolerance in vivo. At this time little is known about the role of TIM‐3 on human T cells. To determine if TIM‐3 similarly identifies and regulates Th1 cells in humans, we generated a panel of mAb specific for human TIM‐3. We report that TIM‐3 is expressed by a subset of activated CD4+ cells, and that anti‐CD3/anti‐CD28 stimulation increases both the level of expression as well as the number of TIM‐3+ T cells. We also find that TIM‐3 is expressed at high levels on in vitro polarized Th1 cells, and is expressed at lower levels on Th17 cells. In addition, human CD4+ T cells secreted elevated levels of IFN‐γ, IL‐17, IL‐2, and IL‐6, but not IL‐10, IL‐4, or TNF‐α, when stimulated with anti‐CD3/anti‐CD28 in the presence of TIM‐3‐specific, putative antagonistic antibodies. This was not mediated by differences in proliferation or cell death, but rather by induction of cytokines at the transcriptional level. These results suggest that TIM‐3 is a negative regulator of human T cells and regulates Th1 and Th17 cytokine secretion.