One of the most important areas of children development is the social skill. Interpersonal problem solving facilitates children`s relationship with peers and creates effective and successful encounter with situation that is achieved through using encounter skills based on awareness, reasoning and rationality. The aim of this study was to investigate the effect of the problem-solving training on social skills in preschool children. The design of present study was quasi experimental with pre-test, post-test and control group. Statistical population of this study consisted of all preschoolers in Kermanshah. Sample of this study consisted of 30 children were selected by the convenient method. They were assigned into two groups (experimental and control group) randomly, each consisting of 15 children. The Shure’s cognitive problem-solving program known as “I can problem solve” was taught through 10 one- hour sessions. Gresham & Elliot`s (1990) Social Skills Rating (parent & teacher`s forms) were used to collect data. The obtained data were statistically analyzed by multivariate analysis of variance and using SPSS version 20 software. The findings showed that in the experimental group, between the pre-test and post-test scores of social skills there is a significant difference (p = 0.001). Therefore, using the problem-solving program is an appropriate method in improving social skills in preschool children. Therefore planning to teach problem solving skills as part of school programs due to its effect on improving the social skills of children has particular importance.