Cooperative learning is today a well known learning method that teachers all over the world use in their classrooms. The aim with the following study is to examine if cooperative learning has an effect on problem solving in mathematics. Problem solving is one of five abilities in mathematics in primary school and the students should be given the best conditions to be able to develop their skills on how to solve a problem. Articles and literature were examined and chosen in order to gain knowledge about the effect of cooperative learning on the ability to solve a problem. The results show that cooperative learning can have a big impact on student’s results and knowledge development in problem solving. Studies have also shown that cooperative learning has a bigger impact on girls’ knowledge development then boys. However, there seems to be greater gains for using cooperative learning when solving a problem contributes to students’ knowledge development.