Perfluorodecanoic acid (PFDA), a C10 fluorine-containing compound, is used widely and found to be present anywhere. However, whether it has reproductive toxicity for fetal Leydig cells and the underlying mechanisms remain unknown. PFDA was investigated for its effects on fetal Leydig cells (FLCs) following exposure to 0, 1, 2.5, and 5 mg/kg/days (gavage to dams) from day 14 to day 21 during gestation. The study showed that in utero medium-dose PFDA (1, 2.5 mg/kg/days) exposure increased fetal body weight. However, PFDA markedly reduced serum testosterone levels, downregulated FLC genes (