Despite changes to breast cancer screening guidelines intended to decrease screening in younger and older women, mammography rates remain high. We investigated physician attitudes towards screening younger and older women. Surveys were mailed to US primary care providers and gynecologists between May and September 2016 (871/1665, 52.3% adjusted response rate). We assessed physician (1) attitudes towards screening younger (45-49years) and older (75+ years) women and (2) recommendations for routine mammography. We used exploratory factor analysis to identify underlying themes among physician attitudes and created measures standardized to a 5-point scale. Using multivariable logistic regression models, we examined associations between physician attitudes and screening recommendations. Attitudes identified with factor analysis included: potential regret, expectations, and discordant guidelines (referred to as potential regret), patient-related hazards due to screening, physician limitations and uncertainty, and concerns about rationing care. Gynecologists had higher levels of potential regret compared to internists. In adjusted analyses, physicians with increasing potential regret (1-point increment on 5-point scale) had higher odds of recommending mammography to younger (OR 8.68; 95% CI 5.25-14.36) and older women (OR 4.62; 95% CI 3.50-6.11). Increasing concern for patient-related hazards was associated with decreased odds of recommending screening to older women (OR 0.68; 95% CI 0.56-0.83). Physicians were more motivated by potential regret in recommending screening for younger and older women than by concerns for patient-related hazards in screening. Addressing physicians' most salient concerns, such as fear of missing cancer diagnoses and malpractice, may present an important opportunity to improving delivery of guideline-concordant cancer screening.