BackgroundDiabetic nephropathy (DN), a common microvascular complication of type 2 diabetes mellitus (T2DM), is an important factor causing chronic kidney disease. However, the relationship between miR‐29a and DN remains unknown. Therefore, a cross‐sectional study was conducted to identify a potential molecular biomarker for DN prevention and management by detecting the serum miR‐29a levels.MethodsThe serum miR‐29a levels were measured in 360 subjects (180 T2DM patients and 180 healthy controls) using quantitative reverse transcription PCR (qRT‐PCR), and other conventional indicators were measured and analysed. A binary logistic regression was used to evaluate the DN risk factors; a receiver operating characteristic (ROC) curve was applied to analyse the diagnostic efficacy of miR‐29a for DN, and a Spearman's rank correlation analysis was used to evaluate the correlation between serum miR‐29a and cystatin C.ResultsThe serum miR‐29 levels in the T2DM patients were higher than those in the healthy subjects and significantly increased with the progression of DN (p < 0.05). Serum miR‐29a and cystatin C are independent predictors of the occurrence of DN. Compared with a single indicator, the combination of serum miR‐29a and cystatin C has better DN diagnostic performance. In addition, the serum miR‐29a levels were positively correlated with cystatin C in the patients with DN (r = 0.521, p < 0.001).ConclusionThe expression of serum miR‐29a was significantly associated with the occurrence and progression of DN and is expected to become a potential biomarker for the diagnosis of DN.