Introduction: Much has been written about medical students' professional identity formation, the process of "becoming" a doctor. During their training, medical students interact with a range of teachers and trainers. Among these are simulated patients (SPs) who role-play patients, assisting students with their communication, procedural, and physical examination skills. With SPs regularly interacting with students, this qualitative study explored their views of students' emerging professional identities at one Australian medical school. SPs' contributions to developing professional identities were also explored. Methods: Fourteen SPswere interviewed individually or in pairs. After template analysis of the transcripts using a priori themes, a follow-up focus group (n = 7) was arranged. Findings: Although being older (implying maturity and more life experience) and exposure to real patients and previous health care experience were identified as contributing to developing an identity as a doctor, SPs recognized that for some, an existing professional identity might impede the development of a new identity. Simulated patients were of the opinion that they contributed to students' professional identities by creating a supportive environment for honing skills, which they did by realistically roleplaying patient scripts, by making their bodies available, and by providing feedback as "patients." Conclusions: Through their authentic portrayal of patients and through their feedback, we are of the opinion that our SPs can contribute to students' developing identities as doctors. As lay individuals who often encounter students longitudinally, we believe that SPs offer a particular lens through which to view students' emerging identities as future doctors.