In response to the COVID-19 pandemic, the American Society of Breast Surgeons and American College of Radiology released a joint statement recommending that all breast screening studies be postponed effective March 26, 2020. A retrospective review of all canceled mammograms at a single tertiary care institution from January 1-August 31, 2020 was performed to evaluate the effect of this recommendation by quantifying both the number and reason for mammogram cancellations before and after March 26, 2020. Utilization of the electronic patient portal for appointment cancellation as a surrogate for telehealth uptake was noted. During the study period, 5340 mammogram appointments were kept and 2784 mammogram appointments were canceled. From a baseline of 30 (10.8%) canceled mammograms in January, cancellations peaked in March (576, 20.6%) and gradually decreased to a low in August (197, 7%). Reasons for cancellations varied significantly by month (P < .0001) and included COVID-19 related (236, 8.5%), unspecified patient reasons (1,210, 43.5%), administrative issues (147, 5.3%), provider requests (46, 1.7%), sooner appointments available (31, 1.1%), and reasons not given (486, 17.5%). In addition, compared to a baseline in January (51, 16.5%), electronic patient portal access peaked in August (67, 34.0%). Screening mammogram cancellations have gradually recovered after early COVID-19 restrictions were lifted and increasing use of electronic patient access appears to be sustained. Consequences for future staging at the time of diagnosis remain unknown. Understanding to what extent the pandemic affected screening may help surgeons plan for post-pandemic breast cancer care.