As a new member of the helper T cell subsets, Th17 cells have triggered more and more interest in exploring their development, regulation, function and therapeutic manipulation in distinct context since they were identified in 2005. This also causes a lot of confusion and debate about the generation and function of Th17 cells, especially their activity in the tumor immunopathology as our understanding grows. However, it is worth asserting that the most confusing part arises from the Th17-associated cytokines including IL-17 and IL-23 rather than the Th17 cells. IL-17 cytokine is not synonymous with Th17-cell subset, although IL-17 is the lineage-signature cytokine for Th17 cells. We will discuss the generation, cytokine profile, genetic control, plasticity and stemness of Th17 cells and address the role of Th17 cells and their associated cytokines in tumor immunity, and further explore the potential immunotherapy by targeting Th17 cells and their cytokines.