Leptin is a hormone expressed mainly in white adipose tissue. It acts on satiety centers in the hypothalamus, and by binding to particular receptor OB-Rb, plays a crucial role in controlling appetite, body weight, fat amount and total energy balance. In this study, a novel single nucleotide polymorphism (SNP), i.e., SNP G-2863A, was identified in the distal promoter region of porcine leptin gene. Totally 780 individuals of Duroc, Yorkshire, Laiwu, Lulai Black breeds, and Landrace × Yorkshire crossbred were genotyped by PCR-SSCP approach. The effects of SNP G-2863A on mRNA and serum protein levels of leptin as well as in driving transcription were examined. The results showed that, except for Duroc and Yorkshire pigs, three genotypes of GG, GA and AA were detected. Allele G occurred with a higher frequency in western breeds and Landrace × Yorkshire crossbred pigs, whereas with a lower frequency in Laiwu pigs. Statistical analysis indicated that there were consistent trends toward higher levels in animals with genotype GG than with GA or AA genotypes in backfat thickness of both Landrace × Yorkshire crossbred and Lulai Black pigs, in backfat leptin mRNA and the circulating serum leptin protein level in half-sibling Lulai Black pigs, and the activity of allele G was significantly higher than allele A (P < 0.01) in driving reporter gene expression. These results suggest that SNP G-2863A is a potential DNA marker for backfat thickness and has a regulatory role in leptin transcription.