This study aimed to examine the effects of social relationship enhancement activities in a mixed age group on the leadership abilities of 5-year-old children. Forty 5-year-old children at two childcare centers in Gyeogsangnam-do participated in the study, and the data collected from these children were analyzed using a repeated measures ANOVA. The dependent variables for both the experimental group and control group were pre-test and post-test leadership scores. The study results showed that social relationship enhancement activities in a mixed-age group were effective in improving leadership as well as sub-factors of leadership including challenges with self-confidence, respect for others, self-control, and problem-solving skills.