Innate lymphoid cells (ILCs) play critical roles during innate immune responses to pathogens and lymphoid organ development. IL-7Ra+ ILC subsets, similar to T helper (Th) cell subsets, produce distinctive effector cytokines. The molecular control of IL-7Ra+ ILC development and maintenance has yet to be dissected. Here we report that GATA3 is indispensable for the development of all IL-7Ra+ ILC subsets and T cells. Gata3 conditional deficient mice have no lymph nodes and are susceptible to Citrobactor rodentium infection. Genome-wide gene analyses indicate that GATA3 regulates similar set of cytokines and receptors in ILC2s and Th2 cells and is critical for the maintenance of ILC2s. Thus, GATA3 plays parallel roles in establishing and regulating both adaptive and innate lymphocytes. To identify GATA3 regulated genes in type 2 innate lymphoid cells by tamoxifen-mediated acute deletion of Gata3 gene.