Since 2009, one-third of all US teacher preparation programs have implemented a new, technology-based teacher assessment—edTPA. Intended to replace traditional measures of initial teaching competency, edTPA utilizes a candidate-curated video lesson and ePortfolio. While research shows that these technology-based tools enhance professional practice, the authors demonstrated that unintended consequences occurred when such tools were incompatible with the cultural contexts implementing them. Employing a multiple-embedded case study, qualitative interviews, focus groups, and field observations (N?=?75) were conducted across eight teacher preparation programs. Findings indicate that policy design and organizational factors influenced how programs culturally made sense of and implemented edTPA’s videotaping and ePortfolio tasks for teacher candidates—substantively or instrumentally. In the process, the authors developed a theoretical and practical understanding of how, and under what conditions, large-scale, technology-based policy tools may be implemented successfully across education contexts.