Melatonin is a strong antioxidant that has previously been observed to increase uteroplacental blood flow and increase postnatal calf growth when supplemented during gestation. The objective of the current study was to examine the effects of melatonin implants on uterine blood flow and subsequent offspring growth. Commercial beef heifers and cows were artificially inseminated and assigned to one of two treatment groups supplemented with (MEL) or without (CON) melatonin from days 180 to 240 of gestation. Total uterine artery blood flow was increased in MEL- versus CON-treated cattle. Fetal and birth weight were not different between treatments. However, at castration, body weight was increased in calves from MEL-treated dams compared with CON-treated dams. Further research on placental vascularization and the mechanism in which melatonin impacts angiogenic factors is necessary to understand the relationship between melatonin and compensatory growth that occurs in postnatal offspring.