γδ T cells are a group of T lymphocytes known as nonconventional T cells. They are able to interact with a diverse range of antigens independent from MHC molecules, start the immune response very fast, and serve as a connection between innate and adaptive immunity. These immune cells are categorized into different subsets in both humans and mice and are localized in different body parts due to their specifications. Vγ9Vδ2T cells are the most common subtype of γδ T cells against infections and cancers. These cells can recognize both endogenous and exogenous phosphoantigens that result in their activation. These molecules are also used for γδ T-cell expansion methods to increase the number of γδ T cells for being used in immunotherapy purposes. Many clinical trials showed the effectiveness of various γδ T cell-based cancer immunotherapy approaches against different cell lines. γδ T can also be used in other treatment approaches such as bispecific nanobodies, CAR-T-cell therapies, and cancer vaccines. Besides all the beneficial features of γδ T cells, it should be considered that some studies reveal the pro-tumorigenic activities of these cells. IL-17-releasing γδ T cells are the most common subset among different γδ T cells that show pro-tumorigenic activity by mechanisms such as increasing angiogenesis and cell permeability and inducing immunosuppression. Due to the anti-tumor and pro-tumor activities of γδ T cells, using them in studies and clinical trials should be done by considering the possibility of unexpected adverse results.