INTRODUCTION: Studies have shown the regulatory role of Leptin in bone formation, its expression in adipose tissue as well as increased levels in circulation following the adminstration of inflammatory stimuli such as lipopolysaccharides (LPS). However, there is little data evaluating the role of Leptin in inflammatory periapical lesions. The aim of this study was to evaluate the presence and concentration of Leptin in chronic periapical lesions. MATERIALS AND METHODS: Chronic periapical lesions with different sizes were collected during periapical surgery of the mandibular molars from twenty patients and cultured for 72 hours. The ELISA method determined the concentration of Leptin in supernatant fluids of explants cultures. Statistical analysis was performed using non-parametric tests (Mann-Whitney U, Chi-Square and Spearman’s Correlation Coefficient). RESULTS: Leptin was found in all samples with the average concentration of 405.55±102.98 (pg/mL). There was no significant correlation between the concentration of Leptin and BMI, and the diameters of lesions. CONCLUSION: Leptin can be considered an inflammatory mediator and is likely to have a role during the early phases of dental periapical lesions.