gamma delta T cells are one of the three immune cell types that express antigen receptors. They contribute to lymphoid antitumor surveillance and bridge the gap between innate and adaptive immunity. gamma delta T cells have the capacity of secreting abundant cytokines and exerting potent cytotoxicity against a wide range of cancer cells. gamma delta T cells exhibit important roles in immune-surveillance and immune defense against tumors and have become attractive effector cells for cancer immunotherapy. gamma delta T cells mediate anti-tumor therapy mainly by secreting pro-apoptotic molecules and inflammatory cytokines, or through a TCR-dependent pathway. Recently, gamma delta T cells are making their way into clinical trials. Some clinical trials demonstrated that gamma delta T cell-based immunotherapy is well tolerated and efficient. Despite the advantages that could be exploited, there are obstacles have to be addressed for the development of gamma delta T cell immunotherapies. Future direction for immunotherapy using gamma delta T cells should focus on overcoming the side effects of gamma delta T cells and exploring better antigens that help stimulating gamma delta T cell expansion in vitro.