Environmental estrogen exposure has increased dramatically over the past 50 years. In particular, prenatal exposure to estrogen causes many congenital diseases, among which reproductive system development disorders are extremely serious. In this study, the molecular mechanism of hypospadias and the therapeutic effect of genistein (GEN) were investigated through in vivo models prepared by Di-(2-ethylhexyl) phthalate (DEHP) exposure between 12 and 19 days of gestation. With increased DEHP concentrations, the incidence of hypospadias increased gradually. DEHP inhibited the key enzymes involved in steroid synthesis, resulting in decreasing testosterone synthesis. At the same time, DEHP increased reactive oxygen species (ROS) and produced inflammatory factors via NADPH oxidase-1 (NOX1) and NADPH oxidase-4 (NOX4) pathways. It also inhibited Steroid 5 α Reductase 2 (Srd5α2) and decreased dihydrotestosterone (DHT) synthesis. Additionally, DEHP inhibited the androgen receptor (AR), resulting in reduced DHT binding to the AR that ultimately retarded the development of the external reproductive system. GEN, a phytoestrogen, competes with DEHP for binding to estrogen receptor β (ERβ). This competition, along with GEN's antiestrogen and antioxidant properties, could potentially reverse impairments. The findings of this study provide valuable insights into the role of phytoestrogens in alleviating environmental estrogen-induced congenital diseases.