Abstract: The principal aim of this study was to evaluate serum leptin concentrations and to analyze the interaction between serum leptin levels and C-reactive protein (CRP) levels, hematological parameters in neonates with bacterial septicemia. We studied 40 neonates with bacterial septicemia and 20 controls. The mean concentration of serum leptin, CRP levels, and immature/total neutrophil (IT) ratio in newborns with septicemia were significantly higher than those of controls. Although there were positive correlations between serum leptin levels and serum CRP levels in the septicemic group at the start, there were no correlations between serum leptin levels and other hematological parameters. These results suggest that leptin is not only an adipostatic hormone but also a stress-related hormone.