Successful medical device design necessitates an understanding of stakeholder-driven requirements early in a design process to assure device safety and usability, and support successful and positive patient experiences. Prototypes can be used during stakeholder engagement in the design front end to gather the information that will inform design decisions. However, an understanding of medical device industry practices for front-end stakeholder engagement with prototypes is lacking. Through interviews with medical device design practitioners, this study explored the variety of stakeholder groups engaged by design practitioners, prototype types used during stakeholder engagements, and settings in which engagements occurred during front-end design activities. This study describes the 14 types of stakeholders, 14 types of prototypes, and six types of settings described by practitioners as well as patterns across engagement strategies, stakeholders, prototypes, and/or settings during front-end activities. These outcomes can contribute to broadening designers' stakeholder engagement planning and practices.