Workplace learning in industry is perceived to have a powerful influence on the development of students engineering identity. But, teachers also observed vast developmental differences between students during workplace learning. To find explanations for these differences, we studied students identity development during workplace learning using a self-guiding and mentoring model. Research questions are: (1) To what extent do bachelor engineering students develop their engineering identity during workplace learning? (2) What are students developmental models? (3) Can different effects of these models on student identity development be found? Participants were 256 third-year bachelor student engineers. The data were collected with two written questionnaires, one before and one after workplace learning. Results showed, first, a significant incline and decline on the two aspects of identity development, clarity and identification. Second, combined achievement on the two aspects showed a sort out into four different development groups. Students entering workplace learning with a low identity score proved to catch up, while those entering with a high score slowed down and developed less, indicating a non-successful preparation for workplace learning. We recommend that students professional identity development should be acknowledged and explicated in the course design so it gets greater and explicate attention during the preparation, during workplace learning, and in the final year. For this purpose a system of career conversations could