MDM2 protein is an important regulator of the p53 pathway and has a large effect on the anti-tumorigenic activity of the p53. Presently, we aimed to analyze the possible association of p53 and mdm2 in the development and progression of non-small cell lung cancer. In addition, impact of an important gene promoter polymorphism of MDM2 (T309G, rs 2279744) on its gene expression and ultimately of the TP53 was investigated in non-small cell lung cancer patients. A case-control study using peripheral blood samples of 100 non-small cell lung cancer patients and 100 cancer free healthy controls was conducted. Expression profile of MDM2 and TP53 gene were evaluated by using quantitative real time polymerase chain reaction assay, and MDM2 promoter polymorphism were analyzed by amplification refractory mutation system polymerase chain reaction. Non-small cell lung cancer patients expressed more than 6-fold increased mdm2 and about 7-folds decreased in p53 expression levels compared to healthy controls. Higher fold change increase of mdm2 and/or decrease of p53 were associated with advanced status and poor clinical outcome of the patients. A significant increase in mdm2 of about 14-folds and decrease in p53 of about 16.5-fold were observed among patients with MDM2 (309GG) genotype vs just 2.2-fold increase in mdm2 and 1.9-fold decrease in p53 among patients with MDM2 (309TT) genotype. In conclusion, present study demonstrated that MDM2 (309 T > G) polymorphism may be one of the important factors for the increased expression mdm2, which was associated with down-regulation of p53 at messenger RNA (mRNA) level and ultimately may contribute in the poor clinical outcome of the non-small cell lung cancer patients, thus may prove as a promising target for the treatment of non-small cell lung cancer at molecular level.