This research concerns the design, implementation and evaluation of a blended training course for interpreter trainers. Complex issues pertaining to professional development in a rich web-based learner-centered environment are addressed. Findings confirm a socioconstructivist design within which learners developed the expected skills and knowledge specified in the learning outcomes. Faculty, acting as cognitive and practitioner models, viewed this new teaching experience positively. The use of a design-based research approach led to the formulation of a set of design rules readily usable in similar adult training contexts. Future research will further investigate the potential of the TPACK framework to shed light on faculty's techno-pedagogical competencies.