Longitudinal studies on children's and adolescents' psychological reactions to conflict-related traumatic events in low- and middle-income countries are scarce. The present study aimed to analyze children's and adolescents' responses to conflict-related potentially traumatic events (PTEs) and the impact of the number of different types of PTEs on psychological symptoms and resilience over time. We investigated the presence of psychological symptoms and resilience, defined as low levels of symptoms and high levels of hope, in a sample of 597 conflict-affected children and adolescents allocated to a waiting list condition in four randomized trials conducted in Burundi, Indonesia, Nepal and Sri Lanka. A decrease in functional impairment (p < 0.001), symptoms of PTSD (p < 0.001), anxiety (p < 0.001), depression (p = 0.052), and an increase in social support (p < 0.001), was observed over a six-month follow-up. More than one third of children and adolescents (34.6%) exposed to conflict-related traumatic events improved at follow-up. Levels of hope did not significantly change. Improvement in psychological symptoms and resilience were significantly associated with the number of different types of PTEs experienced before study entry. This study showed that children and adolescents have the capacity to react to multiple traumatic events, and that the number of different types of traumatic events has an impact on resilience mechanisms. This will help differentiate the choice and focus of psychosocial interventions according to the amount of traumatic events experienced by children and adolescents, and will inform the development and testing of new psychosocial interventions.