The present study was conducted to investigate the effectiveness of teaching philosophy to children on social competence and emotional expressiveness of 9-12 year old children. The current study was a semi-experimental application with a pre-test-post-test design with a control group and a two-month follow-up period. The statistical population of the research included children aged 9 to 12 who were studying in the fourth, fifth and sixth grades of primary school in the academic year of 2022-2023 in Tehran. In this research, 35 children aged 9 to 12 were selected by purposeful sampling and randomly assigned to experimental and control groups (18 children in the experimental group and 17 children in the control group). The children in the experimental group received the intervention of teaching philosophy to children during twelve weeks in twelve 75-minute sessions. Emotional Expression Scale of Children (EESC) and Social Competence Scale (SCS) were used in the present study. The data were analyzed through mixed ANOVA via SPSS23 software. The results showed that teaching philosophy to children has significant effect on the social competence (p<0.0001, Eta=0.63, F=51.17) and emotional expressiveness (p<0.0001, Eta= 0.63, F=57.76) in the 9-12 year old children. Based on the findings of the research, it can be concluded that teaching philosophy by introducing students to cooperation and thinking skills, improving communication and social responsibility, developing critical thinking and discovering cognitive and perceptive abilities can be used as an efficient method to improve social competence and emotional expressiveness of children.