Guidelines recommend patients be informed of their incidental results (IR) when undergoing genomic sequencing (GS), yet there are limited tools to support patients' decisions about learning IR. The aim of this study is to develop and test the usability of a decision aid (DA) to guide patients' selection of IR, and to describe patients' preferences for learning IR following use of the DA. We developed and evaluated a DA using an iterative, mixed-methods process consisting of (1) prototype development, (2) feasibility testing, (3) cognitive interviews, (4) design and programming, and (5) usability testing. We created an interactive online DA called the Genomics ADvISER, a genomics decision AiD about Incidental SEquencing Results. The Genomics ADvISER begins with an educational whiteboard video, and then engages users in a values clarification exercise, knowledge quiz and final choice step, based on a 'binning' framework. Participants found the DA acceptable and intuitive to use. They were enthusiastic towards GS and IR; all selected multiple categories of IR. The Genomics ADvISER is a new patient-centered tool to support the clinical delivery of incidental GS results. The Genomics ADvISER fills critical care gaps, given the health care system's limited genomics expertise and capacity to convey the large volume of IR and their myriad of implications.