Background and objectives: the aim of the present investigation was to describe the association of this single nucleotide polymorphism (SNP) with fasting glucose levels, serum adipokine levels and diabetes mellitus. Methods: the study involved a population of 1,002 adult obese subjects. Measurements of anthropometric parameters, blood pressure, fasting blood glucose, C-reactive protein (CRP), insulin concentration, insulin resistance (HOMA-IR), HOMA-B, lipid profi le and adipocytokines levels were performed. Genotype of MTNR1B gene polymorphism (rs10830963) was evaluated. Results: fasting glucose levels (GG: 101.5 ± 19.1 mg/dl vs GT: 103.5 ± 8.1 units vs TT: 107.2 ± 8.0 mg/dl; p = 0.01) and HOMA-IR (GG: 3.1 ± 1.6 units vs GT: 3.4 ± 1.1 units vs TT: 3.7 ± 1.0 units; p = 0.02) were higher in subjects with GG genotype than in other genotypes. Total adiponectin levels (CC: 20.5 ± 8.4 ng/dl vs CG: 21.8 ± 5.4 ng/dl vs GG: 15.4 ± 1.4 ng/dl; p = 0.02) and HOMA-B (CC: 2.3 ± 0.8 units vs CG: 2.2 ± 1.1 units vs GG: 1.9 ± 0.9 units; p = 0.01) were lower in subjects with GG genotype than GC or CC genotypes. Logistic regression analysis showed an increased risk of hyperglicemia (OR = 1.31, 95% CI = 1.12-2.78, p = 0.03) and diabetes mellitus (OR = 1.37, 95% CI = 1.14-2.86, p = 0.04). Conclusions: this study showed that the MTNR1B rs10830963 polymorphism was associated with increased fasting glucose levels, HOMA-IR, and risk of DM2. This SNP was associated with decreased adiponectin levels and HOMA-B.