The present study sought to investigate the effectiveness of a behavior management training package based on choice theory in improving the quality of parent-child relationship. This study had a single-case design which was undertaken with concurrent multiple baseline and a two-month follow-up. The statistical population of the study was comprised of all male ninth graders studying at junior high schools in Javanrud city in 2020-21 school year from among whom 3 students were selected via purposeful sampling method using inclusion criteria and the Parent-Child Relationship Quality Scale (PCRS). Each group, including students and their parents, received 12 separate training sessions which were previously designed and validated by the researchers. Data were analyzed by Visual drawing, Reliable change index (RCI), recovery percentage formula and Cohen’s d effect size. Findings showed that the implementation of behavior management training package based on choice theory had a clinically and statistically significant effect on improving the quality of parent-child relationship (both parent-child scales) (P <0.05). Therefore, it is recommended that the trainings of this behavior management package, which are based on the educational-therapeutic foundations of choice theory, be used individually and in groups by family care institutions and counseling centers of various organizations, including education and welfare.