Breast cancer is the most common malignancy in women. Interleukin-2 (IL-2) plays a key role in the proliferation of T cells and natural killer cells. It has been reported that polymorphisms in the IL-2 gene are associated with various cancers. The aim of this study was to examine the effect of polymorphisms in the IL-2 gene on the development of breast cancer in the Chinese population. IL-2-330T/G and +114T/G polymorphisms were assessed in 638 breast cancer cases and 682 age-matched healthy controls. Data were analyzed using the chi-square test. Results showed that individuals with -330TG genotype and -330GG genotype had significantly increased susceptibility to breast cancer (Odds ratio [OR]=1.42, 95% confidence interval [CI]: 1.10-1.79, p=0.0021 and OR=2.26, 95%CI: 1.53-3.30, p<0.0001). The +114T/G polymorphism did not show any correlation with breast cancer. In addition, when analyzing the survival time of breast cancer patients with IL-2-330T/G polymorphism, cases with a -330G allele had significantly shorter survival time compared with wild-type patients (p=0.002). These results suggested that polymorphism in the IL-2 gene was associated with increased susceptibility to breast cancer and could be used as a prognostic marker for this malignancy.