This study investigated the effect of a high-fat (HF) diet on protein expression of leptin and its receptor in the gonads of dams and their offspring. Female Wistar rats were fed a HF diet (30% fat) or a standard breeding (BD) diet (5% fat) during pregnancy and lactation. At 21 days of lactation, mothers and both sexes of prepubertal offspring were killed by decapitation. The protein expression of leptin and its receptor was assayed by Western blot and immunohistochemistry in gonadal, periovarian, and epididymal white adipose tissue (WAT). We demonstrated that leptin protein expression in ovary, and both leptin and ObRb expression in periovarian WAT was decreased in HF dams compared with BD animals. Immunohistochemistry showed lower leptin expression in growing antral follicles and corpora lutea of HF dams. Conversely, in both gonads and epididymal WAT of HF offspring, leptin and its receptor were significantly higher expressed compared with BD. Immunolocalization of leptin system in HF offspring gonads showed higher expression in growing and antral follicles of the ovary, seminiferous tubules, and interstitial tissue of testes. In conclusion, high gonadal and gonadal-WAT expression of leptin system was observed in the offspring of dams fed a HF diet during pregnancy and lactation.