This self-study was designed to explore problem-based learning (PBL) as an instructional approach in the context of a pre-service science education methods course. Through the development and implementation of PBL curriculum, the author's goals were to improve her classroom practice and her understanding of that practice, to contribute to the knowledge base of teaching and learning, and to immerse students in authentic learning experiences that would encourage them to adopt an inquiry-based approach to teaching and learning. In studying her own practice, the author adopted classroom-based action research as a strategy to explore PBL. Data collection methods and sources included field notes, interviews, and student-generated documents. The author describes how many aspects of her pedagogical content knowledge (conceptions of the purposes for teaching subject matter, knowledge of students' understanding, curricular knowledge, and knowledge of instruction and assessment) and classroom practice were transformed.