This study investigated the relationship between traumatic life stress, trust, and prosocial behavior as a positive mental health outcome in Syrian refugee children in Canada. Trust is a resilience factor shown to promote adjustment after resettlement. The specific goals of the study were to test the influence of refugee children's traumatic life stress on their prosocial behavior and the mediating role of trust in this link. Five- to 12-year-old Syrian refugee children (N = 124) and their caregivers (N = 51) who recently resettled in Canada participated in this study. Children retrospectively reported their experiences of traumatic life stressors, and caregivers reported their children's current level of trust and prosocial behavior using questionnaires. Traumatic life stress (e.g., witnessing violence and conflict, separation from family, death of family members) was negatively related to refugee children's trust in others, while trust was related to more prosocial behaviors, confirming its mediating role. These results suggest that experiencing more traumatic life stressors is associated with less prosocial behaviors as a positive mental health outcome through lower levels of trust. The current findings suggest that fostering trust may be a promising avenue for intervention to promote prosocial behavior and resilience in refugee children who are resettling in a new society.