Objective: In this study, we performed an updated meta-analysis by summarizing all available relevant association studies to evaluate whether the murine double minute-2 (MDM2) T309G polymorphism is associated with risk of leukemia and to determine its prognostic effect. Material and Methods: Studies published in PubMed, Embase and the Cochrane Controlled Trial Register were searched till June 2014 using the search terms ‘MDM2', ‘polymorphism' and ‘leukemia'. Results: Eleven studies were included in this meta-analysis, with a total of 2,478 patients accrued. There were 8 studies providing data on single nucleotide polymorphism at position 309 (SNP309) and risk of leukemia and 7 studies providing data on SNP309 and overall survival. Our analysis showed that patients having G/G mutations had a significantly higher risk of developing leukemia (HR 1.90, 95% CI 1.56-2.31, p < 0.00001), while the association between G/T and leukemia was not significant (HR 1.18, 95% CI 0.96-1.45, p = 0.11). In addition, SNP309 was not significantly associated with patient survival (HR 1.29, 95% CI 0.79-2.13, p = 0.31). Conclusions: Our meta-analysis showed that the MDM2 T309G variation, especially homozygous G/G, might be associated with an increased risk of leukemia. Additional studies are needed to confirm the findings as well as to understand the underlying mechanisms.