Abstract: Objective To study the association of nt3434 A→G mutation in mitochondrial DNA NADH dehydrogenase 1 subunit (ND1) gene with diabetes mellitus. Methods PCR-RFLP was used to detect the nt3434 A→G variant of mtDNA ND1 gene in 216 diabetic patients and 203 healthy control individuals. Characteristics of mutation and clinical indicators in nt3434A→G family were analyzed. Results nt3434A→G mutation was detected in one diabetic patient but not found in NC group. This patient had low insulin secretion, low BMI, and elevated serum lactate acids. No significant difference was found in the mutation frequencies between these two groups. nt3434 A→G mutation was also detected in this patient’s sister and daughter, who were normal glucose tolerance and had slightly elevated serum lactate acids levels. Conclusion Further investigation would be helpful to answer whether nt3434A→G mutation of mitochondrial DNA ND1 gene is associated with an increased risk of diabetes.