This research aimed to examine the effect of a problem-based learning approach in comparison to traditional learning approaches. In this context, the question "What is the effect size of problem-based learning on students' attitudes?" was tried to be answered. Among 190 studies made in national and international field between the years 2006 to 2013, 19 theses and 6 articles, in which pre-test and post-test experimental design was applied, were examined in this meta-analysis according to inclusion criteria. As a result of analytic evaluation, the effect size value of the problem-based learning on attitudes in relation to a random effects model was measured to be 0.7195. Thus, it can be said that this value had a medium effect size according to the classification levels of Thalheimer and Cook. It was concluded from these results that problem-based learning approaches were more effective when compared to traditional teaching techniques.