Background: Children who are deprived from parental care for any reason are eligible to enter the foster care. Foster care children are at increased risk for developing emotional and behavioral problems for a variety of reasons. This study aimed at assessing the relationship between self-esteem and aggressive behavior among foster care children at Minia governorate. Research Design: A descriptive correlational research design was utilized in this study. Study subjects: 51 foster care children in age group 6-12years.were included in the study. Tools; Aggressive behaviors scale and Hare Self-Esteem Scale were used. Results: Majority of participants were males. More than two thirds of the foster children (74.5%) had low level of self-esteem and foster boys had high mean scores of physical aggression than girls and there was a significant negative correlation between aggression and self-esteem (r = 0.33). Conclusion: there was a significant negative correlation between aggression and self-esteem. Recommendation: Frequent assessment of aggressive behavior and self-esteem among foster care children are needed.