Assessment for learning approaches, such as peer review exercises may improve student performance in summative assessments and increase their satisfaction with assessment practices. We conducted a mixed methods study to evaluate the effectiveness of an oral peer review exercise among post-graduate students. We examined: (1) final assessment grades among students who did and did not take part in the peer review exercise; (2) student perceptions of the impact of the peer review exercise; and (3) student understanding of, and satisfaction with, this new assessment practice. We found that students who took part in the exercise had a significantly higher mean grade in a subsequent summative oral presentation assessment than students who did not take part in the exercise. Students gained a better understanding of assessment and marking criteria and expressed increased confidence and decreased anxiety about completing the subsequent summative assessment. Assessment for learning improves academic attainment and the learning experience in postgraduate students.