The tutor is an essential part of problem based learning (PBL). However, tutor characteristics and role are inconsistent. Meta-analysis was used to investigate both the role and training of PBL tutors as moderators of student learning. Weighted effect sizes were calculated on student outcomes with a modest favorable overall effect size for PBL; a vote count shows favorable results as well. Results indicate a mixture of peers and instructors do best when compared to peers and instructors alone. Tutor training appears to make a difference by itself, but when considered with tutor background, tutor training does not appear to moderate student learning. A framework for study factors and recommendations for future work are provided.