In the quaternary education sector, a variety of trainers and instructors are active, offering diverse learning scenarios. With titles such as coach or learning consultant, they attempt to distinguish themselves in the market, although this does not provide any conclusions about their competencies or quality. In the theoretical debate, it is unclear what skills and knowledge a professional trainer must possess. Using the Delphi method, this work investigates which competencies a trainer or instructor must demonstrate and what strategies they employ to be considered professional. The theoretical debate on professionalization is contrasted with the experiential knowledge of trainers, personnel developers, and heads of educational institutions.