Objective To examine the effect of a change in U.S. Preventive Services Task Force (USPSTF) screening guidelines on mammography rates in the United States. Principal Findings In 2010, the year following the change in guidelines, 12‐month mammography prevalence among women aged 40–49 years fell by 2.09 percentage points (95 percent confidence interval [CI]: −2.87 to −1.31) from 54.63 percent in 2008. For women aged 50–74 years, and aged 75 years and older, 12‐month screening rates were 2.21 (95 percent CI: −2.65 to −1.77) and 3.60 (95 percent CI: −4.48 to −2.70) percentage points lower than those in 2008. In 2012, for women aged 40–49 years, 12‐month prevalence fell to 52.51 percent, a decline of 2.12 percentage points (95 percent CI: −2.79 to −1.32) relative to screening rates prior the USPSTF announcement. For women aged 50–74 years and aged 75 years and older screening rates were 2.45 (95 percent CI: −2.96 to −2.07) and 5.71 (95 percent CI: −6.61 to −4.81) percentage points lower, respectively, in 2012 than in 2008. Conclusion This study demonstrates an immediate and lasting reduction in the rates of breast cancer screening among women of all age groups after the 2009 revision of screening guidelines by the USPSTF.