Widespread consumption of canned tuna fish since the 1950s may explain some of the increase in breast cancer prevalence in the United States and Europe. Although canned tuna is the primary source of human exposure to methylmercury, its role as an estrogen activating metalloestrogen has been overlooked in the etiology and incidence of breast cancer. Carcinogenic theory asserts that increased exposure to estrogen elevates the risk of breast cancer. The purpose of this population-based, case control study was to examine the association between canned tuna consumption, total blood mercury, and breast cancer in the NHANES 2003-2006 surveys. A multivariable logistic regression model representing 138,747,398 U.S. adult females, controlling for covariates, was applied to investigate whether canned tuna consumption or blood mercury level had a relationship to breast cancer. According to study results, women who reported eating canned tuna at one level of increased frequency out of 11 had a 6.8% increased odds of being diagnosed with breast cancer (p =0. 000 OR 1.068 and 95% CI 1.067-1.069). Women with only a 0.01 Ug/L increase in total blood mercury level were found to have a 0.2% increased odds of being diagnosed with breast cancer (p =. 000 OR 1.002 and 95% CI 1.002-1.003). Additional research individuating the canned tuna fish variable in nutrition, fish, mercury, and breast cancer studies is recommended. This research contributes to positive social change by providing evidence to improve understanding and specification of canned tuna fish in future research and better identification of methylmercury levels in canned tuna fish for public knowledge.