Background: There is now an abundance of global evidence demonstrating serious developmental and psychological problems associated with placement in residential care which reflected in the form of poor self-esteem, aggressive behavior, academic failure and later on, personality disorder. Aim: The study aimed to evaluate the effect of social skill training program on self-esteem and aggression among children in residential institutions in Port-Said City. Subjects and Methods: A quasi-experimental research design was used. The present study was carried out at all governmental residential institutions in Port Said city namely,Al-Nessaieya le Tahseen Al- Seha, Dar Alkaserat, Kafalit Al-Yateem, and ApnaaRamses. The subject of the study compromised 57 children, 36 were males and 21 were females. Three tools were utilized to collect data in this studywhich are Socio-demographic data questionnaire, Self-esteem inventory scale, and Aggressive behavior scale for children. Results: The study revealed that almost half of the studied children had low self-esteem and the mean scores of verbal aggression among the studied children were slightly higher than mean scores of physical aggression Also, there was a positive effect of the social skills training program in enhancing self-esteem levels and slightly decreasing physical aggression but there was no effect found regarding verbal aggression. Conclusion: The study concluded that there was a significant effect of social skill training program on enhancing self-esteem and slightly decreasing physical aggression, while it had no effect on verbal aggression. Recommendations: broad-based psychosocial intervention programs for resident children and rehabilitation programs are mainly recommended to enhance self-esteem and minimize aggressive behavior among children