The association between bone mineral density (BMD) and breast arterial calcification (BAC) remains poorly understood and controversial. The objective of this article is to examine the association between BMD and BAC in a large cohort of postmenopausal women undergoing routine mammography. A cross-sectional analysis of baseline data from a multiethnic cohort was performed. The setting for this analysis is an integrated health care delivery system in Northern California in the United States. A total of 1273 women age 60 to 79 years (mean age, 67 years) were recruited within 12 months of screening mammography. A BAC score (mg) was obtained from digital mammograms using a novel densitometry method. BAC presence was defined as a BAC score greater than 0 mg, and severe BAC as a BAC score greater than 20 mg. Overall, 53% of women had osteopenia and 21% had osteoporosis. The prevalence of BAC greater than 0 mg was 29%, 30%, and 29% among women with normal BMD, osteopenia, and osteoporosis, respectively (P = 0.98). The prevalence of BAC greater than 20 mg was 5%, 3%, and 5% among women with normal BMD, osteopenia and osteoporosis, respectively (P = .65). The odds ratios (ORs) of BAC greater than 0 mg vs BAC = 0 mg after multivariable adjustment were 1.09 (95% CI, 0.81-1.48; P = .54) for osteopenia and 0.99 (95% CI, 0.69-1.48; P = .98) for osteoporosis. The adjusted ORs for BAC greater than 20 mg vs BAC 20 mg or less were 1.03 (95% CI, 0.52-2.01; P = .93) for osteopenia and 1.89 (95 CI, 0.81-4.47; P = .14) for osteoporosis. Our findings do not support an association of either osteopenia or osteoporosis with BAC presence or severity among postmenopausal women.