Objective To investigate the associations of serum levels of microRNA-155 (miR-155), microRNA-21 (miR-21), chemerin and leptin with insulin resistance (IR) in obese patients with diabetes mellitus.Methods A total of 138 patients with type 2 diabetes mellitus (T2DM) admitted to the Second Affiliated Hospital of Shandong University of Traditional Chinese Medicine from January 2022 to April 2023 were selected, including 73 obese patients (obese group) and 65 non-obese patients (non-obese group). In the obese group, there were 45 cases with IR (IR group) and 28 cases without IR (non-IR group). The general data, including sex, body mass index (BMI), age, neck circumference (NC), waist circumference (WC), fasting plasma glucose (FPG), triglyceride (TG), fasting insulin (FINS), high-density lipoprotein cholesterol (HDL-C), miR-155, miR-21, chemerin, leptin, and insulin resistance index (HOMA-IR), were collected. Multivariable stepwise Logistic regression was performed to analyze the risk factors for IR in obese patients with T2DM. The receiver operating characteristic (ROC) curve was applied to determine the diagnostic values of miR-155, miR-21, chemerin and leptin for IR in obese patients with T2DM. Pearson correlation coefficients were used to analyze the correlations of miR-155, miR-21, chemerin and leptin with HOMA-IR.Results The level of miR-155 in the obese group was lower than that in the non-obese group (P < 0.05), while the levels of miR-21, chemerin and leptin as well as HOMA-IR in the obese group were higher than those in the non-obese group (P < 0.05). The level of miR-155 in the IR group was lower than that in the non-IR group (P < 0.05), while NC, WC and the levels of miR-21, chemerin and Leptin in the IR group were higher than those in the non-IR group (P < 0.05). Multivariable stepwise Logistic regression analysis showed that high NC [O^R = 1.416 (95% CI: 1.038, 1.932) ], WC [O^R = 1.227 (95% CI: 1.049, 1.435) ], and levels of miR-155 [O^R = 1.763 (95% CI: 1.205, 2.579) ], miR-21 [O^R = 1.932 (95% CI: 1.356, 2.753) ], chemerin [O^R = 2.074 (95% CI: 1.492, 2.883) ] and leptin [O^R = 1.628 (95% CI: 1.246, 2.127) ] were risk factors for IR in obese patients with T2DM (P < 0.05). ROC curve analysis revealed that the areas under the curves of miR-155, miR-21, chemerin and leptin in diagnosing IR in obese patients with T2DM were 0.865, 0.909, 0.874 and 0.871, with the sensitivities being 0.778 (95% CI: 0.614, 0.825), 0.867 (95% CI: 0.792, 0.917), 0.956 (95% CI: 0.713, 0.965) and 0.800 (95% CI: 0.692, 0.917), and the specificities being 0.857 (95% CI: 0.647, 0.903), 0.821 (95% CI: 0.732, 0.914), 0.750 (95% CI: 0.675, 0.928) and 0.893 (95% CI: 0.656, 0.944). The level of miR-155 was negatively correlated with HOMA-IR (r = -0.573, P =0.000), while the levels of miR-21, chemerin and leptin were positively correlated with HOMA-IR (r = 0.531, 0.558 and 0.568, all P = 0.000).Conclusion IR is prevalent in obese patients with T2DM, and high levels of miR-155, miR-21, chemerin and leptin are risk factors for IR among these patients.