Mammographic screening contributes to a reduction in specific mortality, but it has disadvantages. Decision aids are tools designed to support people's decisions. Because these aids influence patient choice, their quality is crucial. The objective of the current study was to conduct a systematic review of decision aids developed for women eligible for mammographic screening who have an average breast cancer risk and to assess the quality of these aids. The systematic review included articles published between January 1, 1997, and August 1, 2019, in the PubMed, Embase, Cochrane, and PsycInfo databases. The studies were reviewed independently by 2 reviewers. Any study containing a decision aid for women eligible for mammographic screening with an average breast cancer risk was included. Two doubleblind reviewers assessed the quality of the selected decision aids using the International Patient Decision Aid Standards instrument, version 3 (IPDASi). Twenty-three decision aids were extracted. Classification of decision aid quality using the IPDASi demonstrated large variations among the decision aids (maximum IPDASi score, 188; mean ± SD score, 132.6 ± 23.8; range, 85-172). Three decision aids had high overall scores. The 3 best-rated dimensions were disclosure (maximum score, 8; mean score, 6.8), focusing on transparency; information (maximum score, 32; mean score, 26.1), focusing on the provision of sufficient details; and probabilities (maximum score, 32; mean score 25), focusing on the presentation of probabilities. The 3 lowest-rated dimensions were decision support technology evaluation (maximum score, 8; mean score, 4.3), focusing on the effectiveness of the decision aid; development (maximum score, 24; mean score, 12.6), evaluating the development process; and plain language (maximum score, 4; mean score, 1.9), assessing appropriateness for patients with low literacy. The results of this review identified 3 high-quality decision aids for breast cancer screening. Cancer 2020;126:2765-2774.Breast cancer is the leading cause of women's mortality worldwide. 1 Screening programs based on mammography lead to a 15% to 20% reduction in specific mortality. 2,3 However, assessing the benefits and harms of these programs requires taking into account the biases and disadvantages of mammographic screening. 2 The most important harms of this screening are false-positive results, overdiagnosis, overtreatment, and radiation-induced cancer. 4 The cumulative risk of a false-positive result ranges from 3% to 63% for a woman exposed to annual mammographic screening between ages 50 and 70 years. 5,6 In this context, clinicians may feel uncomfortable submitting their patients to this screening process without using a shared decision-making process. 7 There is now a consensus that patients should have the opportunity to participate in decisions about their health. 8,9 They should understand whether there are options and the related consequences of these options. Patient preferences should be integrated into decision making. 10 Decis...