Background: As genital gender-affirming surgery (GAS) is a demanding and life-changing intervention, transmen should be able to make choices about the surgical treatment based on outcomes that are most important to them, while taking into consideration the concomitant risks involved. Aim: Develop a decision aid (DA) for genital surgery in transmen (DA-GST) that can assist both transmen and health care professionals (HCPs) in making a well-informed decision about the surgical treatment. Methods: A qualitative focus group study was performed. 5 Focus groups were organized with both HCPs and transmen. These were led by an independent professional moderator. Data collected during these focus groups were analyzed to provide content for the DA. Outcomes: To develop content for a DA-GST. Results: Data collected during the focus groups related to the treatment options, information deemed relevant by transmen, and the arguments for or against each treatment option. Collected items were divided into the following themes: outcome, quality of life, environment, sexuality, and beliefs. Clinical Implications: The tool will be useful in assisting both transmen and HCPs in the shared decision-making process regarding genital GAS by exploring which domains are most relevant for each specific individual. Strengths & Limitations: This DA was developed according to an iterative participatory design approach to fit the needs of both transmen and HCPs. Issues that transmen find important and relevant pertaining to genital GAS were translated into arguments that were incorporated in the DA-GST. The study is limited by the group that had participated. Not all arguments for or against specific surgical options may be covered by the DA-GST. Conclusion: An online DA was developed to support transmen with their decision-making process concerning all surgical options for removal of reproductive organs and genital GAS. Özer M, Pigot GL, Bouman M‐B, et al. Development of a Decision Aid for Genital Gender-Affirming Surgery in Transmen. J Sex Med 2018;XX:XXX–XXX.