In this review, we will present an overview of estrogen actions in the testis from immature and adult animals, with special emphasis on signaling mechanisms involved in the 17β-estradiol regulation of Sertoli cell function in immature rats. 17β-estradiol activates Sertoli cell proliferation in immature rats by a mechanism that involves the translocation of the estrogen receptors ESR1 and ESR2 to the plasma membrane, phosphorylation of epidermal growth factor receptor and activation of mitogen-activated protein kinase 3/1. Activation of the G protein-coupled estrogen receptor (GPER) also induces phosphorylation of mitogen-activated protein kinase 3/1 via epidermal growth factor receptor transactivation, which in turn increases expression of the antiapoptotic protein BCL2 and decreases the expression of proapoptotic protein BAX, indicating an antiapoptotic role of E2-GPER in immature rat Sertoli cells. In conclusion, ESRs and GPER can mediate rapid 17β-estradiol signaling in Sertoli cells, and modulate transcriptional events important for Sertoli cell function and maintenance of normal testis development and homeostasis. Our findings are important to clarify the role of estrogen in a critical period of testicular development and to direct further studies, which may contribute to better understand the causes of male infertility.