Group 2 innate lymphoid cells (ILC2s) are located primarily at mucosal sites and are required for host defense against helminths and other large extracellular pathogens. They require GATA-3 for their development and secrete IL-4, IL-5, IL-9, IL-13, and Amphiregulin following activation. ILCs are classified based on their similarities with different effector T cell subsets. As a result, ILC2s are considered to be the innate equivalent of Th2 cells. ILC2s are activated by myeloid or epithelial cell-derived cytokines and inflammatory mediators, such as IL-25, IL-33, IL-4, TSLP, and Prostaglandin D2 (PGD2). They can be distinguished from other ILC subsets based on their expression of the cell surface markers, ST2/IL-33R, ICOS, IL-17 RB, and KLRG1, along with their unique cytokine expression profile. Like Th2 cells, ILC2s promote type 2 inflammation, alternative macrophage activation, eosinophilia, and goblet cell hyperplasia, as well as tissue repair and remodeling. In addition to their protective functions, ILC2s are also thought to contribute to the pathogenesis of atopic dermatitis, asthma-associated airway inflammation, and lung and liver fibrosis.