Problem-based learning (PBL) is a constructivist method of instruction aligned with the science educational reform movement to increase scientific literacy for all Americans. As such, PBL instruction is an increasingly popular topic for professional development workshops offered to teachers in secondary learning environments. This research presents a case study of four teachers' alignment of classroom practice with constructivist principles after participating in a one-week PBL workshop. Teachers assimilated PBL instruction into their current system of teaching; therefore, despite congruent beliefs, those teachers without a constructivist system of practice taught the PBL method with less alignment to constructivist principles. This discrepancy between beliefs and practice could be addressed by helping PBL workshop participants contemplate how components of PBL encourage reform-based constructivist practices and by assisting teachers with modifying preexisting routines to better assimilate PBL instruction.