How do undergraduate students in engineering conceive of themselves as professionals? How can a course on engineering ethics affect the development of an undergraduate student's professional identity? In this project, students responded to questions about the characteristics and responsibilities of professional engineers. The results indicate that students learn about professionalism primarily from relatives and co-workers who are engineers, and rarely from technical engineering courses. Even before they study engineering ethics, students put honesty and integrity on par with technical competence as an essential characteristic of engineers. In the course, students benefit from cases of actual incidents and from classroom activities that encourage diverse perspectives on moral problems. By analyzing cases in groups and by hearing different perspectives, students build self-confidence in moral reasoning. By the end of the course, some students understand professional responsibility not only as liability for blame but in a capacious sense as stewardship for society.