The cytochrome P450 1A1 gene (CYP1A1), encoding Phase I metabolic enzymes, appeared to be a candidate gene for breast cancer risk. However, studies on the association between polymorphisms in this gene and breast cancer have yielded conflicting results. We performed a meta-analysis to investigate the association with breast cancer of the CYP1A1 polymorphisms T3801C (9,316 cases and 12,714 controls) and A2455G (9,552 cases and 9,320 controls). In the genotype contrast of A2455G, both additive [GG vs AA, P = 0.04, fixed-effects OR 0.72; 95% CI (0.53-0.99), P = 0.95 for heterogeneity] and recessive [GG vs (GA + AA), P = 0.04, fixed-effects OR 0.73; 95% CI (0.53-0.99), P = 0.97 for heterogeneity] models produced significant results in east-Asians. In pre-menopausal women in a worldwide population, significant association between A2455G and breast cancer was also found using both models [additive model: P = 0.02, fixed-effects OR 0.52; 95% CI (0.29-0.92), P = 0.39 for heterogeneity; recessive model: P = 0.02, fixed-effects OR 0.51; 95% CI (0.29-0.90), P = 0.38 for heterogeneity]. Our meta-analysis suggests that an A2455G G/G genotype is associated with a trend of reduced breast cancer risk, both in east-Asian women and in pre-menopausal women worldwide, while the T3801C C allele might not be a risk factor for breast cancer. Larger scale primary studies are required to further evaluate the interaction of CYP1A1 polymorphisms and breast cancer risk in specific populations.