Interleukin-17 (IL-17)-secreting CD8(+) T cells have been described, but they have not been thoroughly studied and they do not have a known role in cancer immunotherapy. We skewed CD8(+) T cells to secrete IL-17 through priming in Th17-polarizing conditions. IL-17-producing CD8(+) T cells demonstrated reduced expression of Eomes and diminished cytolytic differentiation in vitro. However, after adoptive transfer, these cells converted to interferon-gamma-producing effector cells and mediated regression of large, established tumors. This improved antitumor immunity was associated with increased expression of IL-7R-alpha, decreased expression of killer cell lectin-like receptor G1, and enhanced persistence of the transferred cells. This report is the first description of a cancer therapy with IL-17-secreting CD8(+) T cells. These findings have implications for the improvement of CD8(+) T cell-based adoptive immunotherapy.