Adoptive cell therapy (ACT) utilizing either tumor-infiltrating lymphocyte (TIL)-derived T cells or T cells genetically engineered to express tumor recognizing receptors has emerged as a powerful and potentially curative therapy for several cancers. Many ACT-based therapies have recently entered late-phase clinical testing, with several T cell therapies already achieving regulatory approval for the treatment of patients with B cell malignancies. In this review, we briefly outline the principles of adoptively transferred T cells for the treatment of cancer.