Background, the preschool class has in recent years become a compulsory grade in the Swedish schools. At the same time the academic demands in mathematics increased. Simultaneously the Swedish National Agency of Education called Skolverket points out the benefits of learning through play. The purpose of this empirical study is to find out what kind of play-based methods teachers use while teaching mathematics in the preschool classes, and what might cause these selections. By the method of a case study four teachers were observed while combining play and mathematics in their preschool classes. Even individually interviews were made. The results indicated a variety of play-based methods existed in the mathematical activities in preschool classes. Both between schools and teachers. The majority of the teachers based their teaching more on methods with academic learning rather than play. Education, time for planning, experience, academic demands and the teachers view on play all affected the choice of method. As a conclusion we can submit that teachers in the preschool classes use different play-based methods to establish mathematical learning for their students. While teachers can see the gain of working with play there are many factors that influence the play-based method.