This study adopted a pre- and post-intervention design to develop and investigate the efficacy of the social inclusion intervention for pre-schoolers with social communication deficit (SCD). It is based on the operant conditioning theory to promote peer acceptance and positive attitude towards children with SCD for their friendship formation in inclusive preschool settings. The participants were 128 pre-schoolers aged from 3 years 9 months to 6 years 11 months old (Mean age = 4 years 9 months) in Hong Kong. There were 54 children with SCD and 74 without SCD with 71 boys and 57 girls. A quasi-experimental research design was conducted, and quantitative data analysis methods were applied. The data were analyzed using a mixed measures ANOVA, followed by two-way ANOVA and independent samples t test or pair samples t test for further analysis. By comparing the sociometric, observation, and questionnaire data before and after the social inclusion intervention, the changes in the sociometric status, interaction frequency, and questionnaire scores of the participants were analyzed. The results indicated a significant increase in popularity and decrease in peer rejection for social acceptance level (SAL) and gain in mutual friendships (MF), F (1, 124) = 4.74, p < .05, ηp² = .04, for all children (both SCD and non-SCD) in the experimental class. No significant differences were found in the Mutual Social Interaction (MSI) and Social Inclusion Status (SIST) scores for all children in the experimental and control class, ps > .05. The performance across the diagnostic types (SCD versus non-SCD ) were further compared. The results in the SCD group revealed a statistically significant gain in the production of SAL and MF, F (1, 124) = 5.08, p < .05, ηp² = .04, and no statistically significant differences in MSI and SIST, ps > .05. The key findings suggested that the novel intervention in the current study is effective to enhance children’s social acceptance level and friendship formation