The aim of this study was to study the effectiveness of problem solving training on behavioral problems of preschool children with behavioral disorder. The design of present study was quasi experimental with pre-test, post-test and control group design. Statistical population of this study consisted of all preschoolers with behavioral problems in Kermanshah. Sample of this study consisted of 30 children who were selected using convenient sampling method and assigned to two groups (experimental and control group) randomly, each consisting of 15 children. The experimental group was trained by a problem solving program entitled "I can solve the problem". Gresham & Elliot`s (1990) Social Skills Rating (parent & teacher`s forms) was used to collect data. The obtained data were statistically analyzed by multivariate analysis of variance through SPSS software (version 20). The findings showed that there is a significant difference (p = 0. 001) between the pre-test and post-test scores in all sub-scales of behavioral disorder including external, internal and hyperactive behaviors in the experimental group. Using problem-solving program is an appropriate method for improving behavioral disorders in preschool children with behavioral problems. Therefore, the need to pay attention to problem solving skills as part of school programs due to its effect on improving the behavioral problems of children with behavioral disorder is felt.