This study has conducted to reveal the effect of the problem based learning on academic success in the 6th grade math lesson. The working group of the study consists of 79 students who are 6th grade at Ismetpasa Secondary School in Duzce. The study has been designed in the model of pretest-posttest control group. "Mathematics success test" and "Semi-constructed interview form on the problem based learning" have been applied as data collection tool. Data has been tested with the analysis of both covariance and content. There is an important difference between pretest results and posttest results when the pretest points have been controlled. When the opinions of experimental group related to these learning methods have been examined these opinions provide the permanent learning, improve the success and develop the skills on problem solving.