BACKGROUND: While previously researching the educational impacts of single-course and cross-curricular portfolios, investigators noted that student participants described their portfolio activities as positively impacting their growing identities as engineering professionals. These impacts were seen particularly in studies regarding cross-curricular portfolios. PURPOSE (HYPOTHESIS): This study was designed to explicitly investigate identity-related impacts of cross-curricular portfolios and to explore the processes students employed during portfolio construction to identify themselves as budding engineers and as future professionals. DESIGN/METHOD: Engineering undergraduate students attended four weekly workshops where they wrote a professional statement, selected artifacts that demonstrated their engineering abilities, and wrote annotations that explained how the artifacts served as concrete examples of their claims for professional standing. Online surveys were administered at each workshop asking participants about their ongoing experiences of creating their portfolios and sharing these portfolios with their peers. RESULTS: Analysis of the survey responses revealed that participants had two primary frames of reference for the construction of professional identity during portfolio creation. The external frame of reference focused on students’ understanding of the expectations of potential employers and recruiters. The internal frame of reference, which accounted for twice as many responses as the external frame coding, focused on students’ emerging realizations of their own values and interests as professional engineers. CONCLUSIONS: As engineering educators, we often support the external frame of reference in terms of building professional identity. We need to provide students with opportunities to engage the internal frame of reference with which our participants were particularly concerned.