Aim: To determine the influence of metacognitive activities within the PBL tutorial environment on the development of deep learning approach, reduction in surface approach, and enhancement of individual learning self-efficacy. Method: Participants were first-year medical students (N = 213). A pre-test, post-test design was implemented with intervention and control cohorts, with intervention students experiencing a program of metacognitive activities within their PBL tutorials of at least 20 weeks duration. All students completed the Medical Course Learning Questionnaire at the commencement, and again at the completion of, the study. The metacognitive intervention itself consisted of reflection on the learning in PBL coupled with peer- and self-assessment. Results: Self-efficacy was significantly reduced for both control and intervention cohorts at the conclusion of the study. A significant reduction in the adoption of deep and strategic learning approach, matched by a corresponding increase in the use of surface learning, was demonstrated for both cohorts. There was a statistically significant association between high self-efficacy and deep learning approach, with older students over-represented in the group of efficacious deep learners. Conclusion: Over the course of first-year medical studies, students lose self-efficacy and move away from deep-strategic learning approaches towards more surface approaches. The program of metacognitive activities failed to reverse this trend. The substantial swing towards surface learning raises questions about the perceived capacity of PBL curricula to promote deep approaches to learning in dense curricula, and reinforces the importance of personal and contextual factors, such as study habits, workload and assessment, in determining individual approaches and idiosyncratic responses to learning situations.