BackgroundStudents' clinical reasoning can be stimulated by guiding them to use their experiences with patients to develop own illness scripts. Debriefing during hospital shifts invites students to put patient experiences into words, link them to previously acquired knowledge and make connections. ObjectivesTo develop, implement and evaluate a debriefing procedure for nursing internships based on illness script theory and generate corresponding design principles. DesignQualitative design-based research. SettingClinical education in dedicated educational hospital units. ParticipantsNurse educators, nursing students. MethodsFrom a collaboration between nurse educators and a researcher, a short, peer-debriefing procedure was designed, tested and enacted through four cycles of planning, action, evaluation and reflection. Students drew mind maps about patients. Nurse educators and students joined focus group discussions to evaluate outcomes and processes. Mind map and iterative thematic analysis were applied to these data. ResultsAn adjusted design and more extensive design principles resulted. Differences in mind maps were evident over time. Three themes in the process evaluation were established: trigger to reason; energy giving and taking; and form follows function. ConclusionsThis design-based investigation displays how nurse educators could design and implement a debriefing procedure to facilitate students' clinical reasoning skills and how students could learn from this. This method integrates research, innovation and collaboration. The design and enactment under real-life hospital conditions generated design principles for educators and researchers which may be useful for those seeking to improve teaching and learning clinical reasoning in practice. More clarification is needed about the path from design through enactment to real change in practice.