Discovered 30 years ago, γδT cells remain an enigmatic T-cell subset. Although they account for a small portion of the total human circulating T-cell pool, their associations with other immune cells and their potential regulatory roles in related diseases have been explored but still require further investigation. γδT cells which are MHC-unrestricted innate-like lymphocytes with more unique antigen receptors than αβT cells and B cells are considered to bridge innate and adaptive immunity. They have APC functions and initiate adaptive immunity. Due to their distribution in specific tissues, secretion of Th1-, Th2-, and Th17-type cytokines, and other characteristics, they are involved in a variety of physiology and pathology processes. They are barometers in HIV infection. However, different γδT cell subsets play opposing roles in HBV infections, autoimmune diseases, and several types of tumors. Moreover, decidual γδT cells have protective roles during pregnancies by synthesizing several cytokines. This emerging evidence provides an improved understanding of the immune mechanism of infection, autoimmunity, cancer, and other related disorders and better insights regarding the potential roles of γδT cells in immunological therapeutic strategies.