Lung cancer (LC) is the leading cause of cancer-related death, with high incidence and mortality rate. Early diagnosis and treatment of LC are imperative to improve the 5-year survival rate for patients with LC. In recent years, miRNAs as promising biomarkers with high sensitivity and specificity for LC have been studied increasingly. In LC regulatory networks, miRNAs play crucial roles in the occurrence, development and metastasis of non-small cell lung cancer (NSCLC), such as oncogenic factors, tumor suppressors and regulators. Dysfunctional miRNAs perform tumor-suppressive or oncogenic functions in the regulation of cell proliferation, invasion, apoptosis, cell cycle disorder and angiogenesis by negatively regulating target genes. In the present review, the biological process of miRNAs was firstly summarized and recent advances in the mechanism of miRNAs involved in tumor formation and development were described. In addition, the present review concentrated on the latest findings on the miRNAs related with circulating free and extracellular vesicles in the early diagnosis of NSCLC. Additionally, the diagnostic performances of circulating free and extracellular vesicles-associated miRNAs in NSCLC were contrasted. Owing to the increased stability and wide-ranging practical applicability, miRNA may be one promising biomarker for NSCLC diagnosis.