As the design thinking approach becomes more established in the instructional design (ID) discourse, the field will have to reconsider the professional identity of instructional designers. Rather than passively following models or processes, a professional identity rooted in design thinking calls for instructional designers to be dynamic agents of change who use reflective thinking to navigate the design space and develop solutions to ill-structured problems. Graduate programs in ID will also need to prepare students to manage the complexities they will encounter in their professional practice, including the establishment of design precedents, reflective thinking skills, and the foundations of professional identity. This research explored the use of reflective writing assignments in an introductory ID graduate course, with results indicating that most students are able to engage in meaningful reflection in relation to prompts concerning design concepts, experiences, and identity attributes, although no clear patterns of improvement emerged over time. Future directions for research include the use of feedback and the structure of prompts (including frequency of writing assignments and wording of prompts) to support improved student performance.