Spermatogenesis relies on the precise regulation of the survival, self-renewal and differentiation of spermatogonia to provide a continuous supply of differentiating germ cells. The understanding of the cellular pathways regulating this equilibrium remains unfortunately incomplete. This investigation aimed to elucidate the testicular and ovarian functions of the Glucocorticoid-induced leucine zipper protein (GILZ) encoded by the X-linked Tsc22d3-2 gene. We found that GILZ is specifically expressed in the cytoplasm of proliferating spermatogonia and preleptotene spermatocytes. While Gilz mutant female mice were fully fertile, constitutive or male-germ-cell-specific ablation of Gilz led to sterility due to a complete absence of post-meiotic germ cells and mature spermatozoa. Alterations were observed as early as postnatal day (P) 5 during the first spermatogenic wave, and included extensive apoptosis at the spermatogonial stem-cell level, and meiotic arrest after meiotic metaphase I. We also found evidence that c-KIT, a tyrosine kinase receptor which essential for the survival and proliferation of male mitotic germ cells, was mislocalized in Gilz-depleted spermatogonia. We thus argue that GILZ is a determinant survival factor for spermatogonia and may interfere with the c-KIT signaling pathway in a way that remains to be elucidated.