This study sought to compare the metacognitive knowledge profile of weak and strong students in problem solving. For achieving this purpose, one hundred students of the second educational District of Tehran were chosen by cluster sampling. They responded individually to the questions of "the Metacognitive Questionnaire Interview" and in the next step their performance in the pendulum problem solving task was perused. Then the subjects were divided into weak or strong groups based on their performance on the pendulum task. In order to compare their profile in metacognitive knowledge, repeated measures factorial design was utilized. The results indicated that the main effect of factor A (problem solving ability) and main effect of factor B (metacognitive knowledge) were significant. The significance of the main effect of factor A demonstrates that there is a significant difference between weak and strong problem solvers regarding the pendulum task. Furthermore, the significance of the main effect of factor B shows that there are significance differences between categories of students’ metacognitive knowledge. In addition, the interaction effect of A and B factors was significant which is indicative of the fact that there are different metacognitive knowledge profiles in the two groups. In general, the findings show that metacognitive knowledge plays an important role in problem solving.