Problem-based learning (PBL) is a tutorial, student-centered, problem-driven educational strategy adopted by medical and allied health educators to positively influence self-directed learning, critical thinking, and learning behavior. PBL was examined in dietetics education through random assignment of 32 undergraduate dietetics students for two weeks to either a problem-based or a lecture-based case format for the infant and elderly units of a 16-week lifespan nutrition course. Random assignment followed stratification for gender and earlier course examination performance. Expert validation of PBL curricular components and noted differences in discussion structure and information resources verified curriculum distinctiveness. Main outcome measures were pre- and post-Cognitive Behavior Survey scores for memorization, reflection, and positive learning experience scales, unit and course evaluations and unit examination scores. Students in problem-based modules demonstrated greater gains in reflective thinking with stable memorization, suggesting improved critical thinking skills. Tenets that problem-based learning promotes knowledge retention and provides a more positive learning experience were not upheld. Knowledge acquisition was not hindered by a problem-based approach. We conclude that gains in reflective thinking and evidence of increased self-directed learning argue for inclusion of PBL in dietetics curricula and that a problem-based education will help dietitians successfully respond to professional development needs.