The aim of the study was to detect polymorphisms in the leptin gene and to determine the association of these polymorphisms with growth and carcass traits in Nellore cattle. The single nucleotide polymorphisms (SNPs) -1457 (AJ571671:g.-1457A>G) and A59V (AF536174.1:g. 321C>T), as well as the microsatellite BM1500 (3.9 kb downstream), were genotyped. The measures of body weight and ultrasound examinations (rib eye area, back, and rump fat thickness) were performed in 3 different periods of animal management. During the first period, the animals were fed with grass and mineralized salt ad libitum. In the second period, they received grass and concentrate, and in the third, only concentrate. After the slaughter of animals, data were collected for classification and typification of carcasses. No significant association was found between the variables assessed and SNP -1457. Conversely, SNP A59V was associated with rump fat thickness and muscle color post-slaughter. BM1500 was associated with rump fat thickness in the first period (pre-slaughter), subcutaneous fat thickness in the second, weight of the animals in the third, and length of the carcass after slaughter. These results suggest that SNP A59V and the microsatellite BM1500 might be useful for marker-assisted selection in Nellore cattle.