Overweight/obesity has become a worldwide epidemic, and factors such as a sedentary lifestyle and inadequate eating habits directly contribute to the development of this condition. Studies indicate that rapid weight gain at critical development stages, such as the lactation period, is associated with the development of obesity, cardiovascular diseases, and diabetes in the long term. In addition to metabolic changes during adulthood, overweight/obesity may influence reproductive function of the population. In this context, the present study aimed to evaluate postnatal overfeeding effects on male and female Wistar rat reproductive parameters. Postnatal overfeeding was induced by applying the litter reduction method for both sexes. Forty animals were used, divided into four groups: two with normal litters (NL♂ and NL♀) and two with small litters (SL♂ and SL♀). The males were euthanized at 90 days of age, on the same date the females were mated. Females were also euthanized after the 20-day gestation. Metabolic and reproductive variables were analyzed. Regarding males, SL animals showed increased body weight, adiposity, and decreased relative weight of the seminal vesicle, prostate, and epididymis as well as changes in the ITT and OGTT glycemic tests. Concerning females, SL animals presented increased body weight, relative perigonadal fat weight, glucose intolerance as well as modify the vaginal opening and increased weight of female pup. The litter reduction method was efficient in leading to metabolic and reproductive alterations in male and female Wistar rat.