The objective was to evaluate nutritional influence on plasma leptin concentration in prepubertal Nellore heifers. Sixteen calves at birth were assigned to 2 groups:1) calves received a concentrate of ground corn (2% of BW; Treated; n = 8); and, 2) calves received mineral salt without supplementation (Control; n = 8), calves from both groups had access to the cow’s diet. After weaning (5 mo of age), both groups received sugar cane bagasse, citrus pulp and concentrate, but the Treated group also received a 2% of BW ground corn supplement until first ovulation or 22 mo of age. Heifers were weighed weekly to calculate monthly weight gain and blood samples were collected twice a week. Leptin was quantified with a RIA kit; the intra-assay CV were 7.64% for high (6.84 ng/mL) and 2.09% for low controls (0.58 ng/mL); the inter-assay CV were 21% for high and 12% for low controls, and assay sensitivity was 0,229 ng/mL. Data were analyzed by ANOVA with the Mixed procedure of SAS for repeated measures. The weight gain from weaning to puberty was 19.5 ± 0.03 kg/month for Treated and 13.2 ± 0.03 kg/month for Control heifers. The first ovulation occurred when the Treated heifers (n = 5) weighed 398.2 ± 10.6 kg (17.8 ± 1.1 mo) and the Control heifers (n = 1) 361kg (20.1 mo). After the 7th month of age there was a difference (P < 0.0001) in monthly weight between treatments. In both treatments, plasma leptin increased according to age (P < 0.0001). Plasma leptin concentration was greater (P = 0.023) in Treated compared with Control heifers at 13, 14, 16 and 17 mo of age, averaging, respectively, 5.67 ± 0.53 vs. 4.04 ± 0.53 ng/mL, 5.79 ± 0.53 vs. 4.34 ± 0.53 ng/mL, 7.12 ± 0.53 vs 5.21 ± 0.53 ng/mL and 6.74 ± 0.67 vs. 5.11 ± 0.53 ng/mL. The greatest weight gain in Treated heifers was observed close to first ovulation. The greatest plasma leptin concentration in Treated heifers was at the 16th month of age. Thus, supplementing heifers with corn hastened age at first ovulation, which is likely mediated by increased weight gain and leptin concentrations (r = 0.96; P < 0.0001), permissive factors that influence GnRH/LH secretion.