This study sought to determine the effectiveness of administering Child Parent Relationship Therapy (CPRT) (Based on Landreth Model) to mothers in reducing the behavioral problems of their school children. This quasi-experimental research had a pretest-posttest control group follow-up design. The statistical population of the study was comprised of all mothers of primary school students in Dardasht neighborhood in District 8 of Tehran in school year 2016-17. The drawn sample (N=60) was selected by simple random sampling method and was assigned to an experimental (N=30) and a control group (N=30). The instrument included Rutter’s Child Behavior Questionnaire. The experimental group went through a ten-session course on CPRT based on Landreth model and the control group did not receive any intervention. At the end of the training, behavioral problems were measured during posttest and follow-up phases and the data were analyzed via repeated measures ANOVA. According to the results, CPRT was found to be effective in reducing child behavior problems. In fact, CPRT can enhance the sense of self-efficacy and confidence. This, in turn, can boost child-mother relationship and pave the way for reducing children’s behavioral problems.