Endocrine disrupting chemicals (EDCs) in the environment are considered to be a contributing factor to the decline in the sperm quality. With growing evidence of the harmful effects of EDCs on the male reproductive system, we tested the hypothesis that prenatal exposure to an environmentally relevant phthalate mixture adversely affects reproductive outcomes and androgen synthesis. In this study, an environmentally relevant composition of phthalates (15% DiNP, 21% DEHP, 36% DEP, 15% DBP, 8% DiBP, and 5% BBzP) that were detected in urine samples of pregnant women in Illinois, United States, was used. Pregnant CD-1 mice (F0) were orally dosed with a vehicle or the phthalate mixtures (20 µg/kg/day, 200 µg/kg/day, 200 mg/kg/day, or 500 mg/kg/day) from gestational day 10.5 to the day of birth. Then, the indices of the reproductive function of the F1 males born to these dams were assessed. Those male mice prenatally exposed to the phthalate mixture had smaller gonads, prostates and seminal vesicles, especially in the 20 µg/kg/day and 500 mg/kg/day phthalate mixture groups, compared to the controls. Importantly, at the age of 12 months, those prenatally exposed mice had significantly lower serum testosterone concentrations accompanied by the decreased mRNA expression of testicular steroidogenic genes (StAR, Cyp11, and Cyp17) and impaired spermatogenesis. Taken together, this study found that prenatal exposure to environmentally relevant doses of a phthalate mixture caused a life-long impact on the reproduction in male mice.