Copy number variations occur frequently in the genome and are a significant source of human genetic variation accounting for disease. Recently, we discovered a common deletion located in the APOBEC3A and APOBEC3B genes significantly associated with breast cancer in Chinese women. Investigating this locus in other populations would be an expedient way to evaluate the generalizability of the novel finding. We analyzed the APOBEC3 deletion in a large study of 3273 European-ancestry women (including 1671 breast cancer cases and 1602 controls) from the population-based Nashville Breast Health Study. All participants were genotyped using real-time qualitative PCR. Logistic regression was used to derive odds ratios (ORs) and 95% confidence intervals (CIs) for the associations between the deletion polymorphism and breast cancer risk. The APOBEC3 deletion was observed in 12.4% of cases and 10.4% of controls. The deletion was significantly associated with breast cancer risk, with ORs and 95% CIs of 1.21 (1.02-1.43) associated with one-copy deletion and 2.29 (1.04-5.06) associated with two-copy deletion compared with women with no deletion (P for trend = 0.005). The positive association of the APOBEC3 deletion with breast cancer risk was similar for estrogen receptor-positive and estrogen receptor-negative breast cancer and was not modified by known breast cancer risk factors. Results from this study confirmed the association of the APOBEC3 deletion with breast cancer risk among women of European ancestry.