Lung cancer is a common type of cancer that causes a very large public health burden worldwide. Achieving a better understanding of the molecular mechanism underlying the progression of lung cancer is of benefit for the diagnosis, prognosis, and treatment of lung cancer. Here, we first identified dramatically decreased expression of miR-338-5p in lung cancer tissues and cells using quantitative polymerase chain reaction (qPCR) analysis. We then revealed that miR-338-5p inhibited the cell growth and migration of lung cancer cells using cell counting kit 8 (CCK8), EdU, and Transwell analysis. Furthermore, we demonstrated that miR-338-5p inhibited METTL3 expression by qPCR, western blot analysis, and luciferase reporter assay, while upregulation of METTL3 alleviated the role of miR-338-5p in lung cancer cells. We also showed that METTL3 promoted c-Myc expression by increasing the m6A modification of c-Myc, and overexpression of c-Myc restored the inhibition of cell growth and migration of lung cancer cells induced by METTL3 silencing. Ultimately, this research illustrated that modification of the miR-338-5p/METTL3/c-Myc pathway affected cellular progression in lung cancer cells. Collectively, our study revealed the underlying mechanism of miR-338-5p in lung cancer, providing a novel regulatory pathway in lung cancer. There is potential for this pathway to serve as a diagnostic, prognostic, and therapeutic biomarker for lung cancer.