The purpose of this study was to analyse how the interrelationships of interns, clients and mentors lead to success in a project-based learning design virtual internship program. Interns from eleven different university programmes were asked to apply their academic experiences in constructing real projects for clients using a virtual environment while under the supervision of mentors. Data included completed intern projects, intern journals, and mentor and client evaluations. Data were collected over five cohorts, from forty-two cases, six of which are highlighted in this study. Programme design, mentor and client training, and intern performance, are considered. Findings demonstrate that interrelated roles evolve during the virtual internship and project success is related to the co-construction of knowledge between the intern, mentor and client. The study of the functions of these roles leads to implications for the design, development and implementation of a successful virtual internship programme.