Girls between the ages of 9 and 10 begin to experience physical, physiological, and hormonal changes that may lead to internal stress. At this age, children are struggling for autonomy; on the other hand, they may experience emotional instability, and for these reasons, they may be vulnerable in many ways. This experimental study aimed to investigate the effect of resilience training on assertiveness in student girls aged 9-10. Data were collected before, immediately after, and 1 month after the intervention in the control (n = 40) and intervention (n = 37) groups. There was a significant difference between the assertiveness of the intervention immediately (26.80 ± 3.73) and 1 month after the intervention (27.05 ± 3.73), and assertiveness significantly increased in the intervention group (p = 0.0001). Resilience training leads to improvements in assertiveness in student girls aged 9-10.