Introduction: The most common variety of lung cancer is non–small cell lung cancer (NSCLC) accounting for 84% of new cases. Surgery, chemotherapy and radiation are the primary treatment option. Metformin has recently been demonstrated to have an anti-tumour impact on various cancer cells. The goal of this investigation was to determine the growth inhibitory, antiproliferative, cytotoxic, apoptotic and cell cycle arrest properties of metformin HCl oral tablets on the A549 lung carcinoma cell line. Methods: The cells were treated with different dosages of an oral preparation of metformin, with untreated cells used as a control. The Trypan Blue Exclusion Assay was used to determine metformin’s inhibitory and cytotoxic effects. Flow cytometry was used to evaluate apoptosis and cell cycle arrest. Results: In a dose-dependent manner, metformin HCl was able to reduce the viability of treated cells compared to the untreated control. Cell proliferation was considerably inhibited in the treated group with the IC50 dose than in the untreated control group and the IC50 dose showed no cytotoxic effect on L929 cells. Induction of apoptosis and cell cycle arrest was observed in the IC50 dose-treated group by Flow cytometry analysis and data showed metformin oral drug causes early apoptosis and a considerable cell increase in the S phase of the cell cycle. Conclusion: Metformin inhibits cell growth and induces apoptosis and cell cycle arrest in the cell line. A comprehensive proteome examination is required to understand more about the mechanism of action of the oral metformin HCl on cancer cells