Aim: This study aimed to compare HOMA-IR, leptin, and resistin as the risk factors for diabetic nephropathy in the type 2 diabetes mellitus (T2DM) patients with different BMI classifications. Materials and Methods: A total of 309 patients with T2DM were enrolled in this crosssectional study. All participants were divided into three groups according to BMI: the normal weight group (18.5 kg/m(2)=BMI<24 kg/m(2)), the overweight group (24kg/m(2)=BMI<28 kg/m(2)) and the obesity group (BMI=28 kg/m(2)). The clinical information and laboratory examinations were recorded in detail. Leptin and resistin levels were measured using enzyme-linked immunosorbent assay (ELISA). Results: Higher HOMA-IR, leptin and resistin levels were found to be the risk factors for diabetic nephropathy when we made comparisons in the total population (P<0.05). In the normal weight group, logistic regression analysis showed that T2DM patients with higher HOMA-IR (OR=4.210, P=0.001), leptin (OR=2.474, P=0.031) and resistin levels (OR=8.299, P<0.001) had nearly 4-fold, 2-fold and 8-fold risk for diabetic nephropathy, respectively, after adjustments. The receiver operating characteristic (ROC) curves indicated that the area under the curves (AUCs) of HOMA-IR and resistin were 0.699 (95% CI 0.617-0.772) and 0.790 (95% CI 0.715-0.854), respectively, which were significantly larger than the AUC of 0.5 (all P<0.001). However, no significant association was observed between HOMA-IR, leptin, and resistin and renal complications (all P>0.05) in the overweight and obesity groups in both logistic regression and AUC analysis. Conclusion: Higher insulin resistance, leptin and resistin levels were observed as risk factors for diabetic nephropathy in T2DM patients with lower BMI. These were not obvious in the overweight and obese patients.