This study investigates the gender differences in children’s subjective well-being and how optimism and resilience affect children’s subjective well-being. There were 313 students (160 boys and 153 girls) from a primary school in Singapore who participated in the study. The findings revealed that girls had significantly lower subjective well-being as compared to boys. Optimism and resilience were both identified as significant predictors of well-being. However, gender differences were observed only in optimism where girls reported lower optimism than boys. The study underscores the need for schools to focus more on the well-being of children and suggests that interventions centred on optimism might be especially beneficial for girls. The research emphasizes the importance of factoring in gender when devising well-being strategies and provides insights for future research and practice in education.