This stepped-wedge cluster randomized trial conducted in refugee settlements in Uganda assessed the effectiveness of a vignette-based community detection tool (CCDT) compared to standard awareness-raising activities for promoting mental health service use among children and adolescents. Community gatekeepers were trained to use the CCDT to proactively detect children with mental health concerns and direct them to services provided by Transcultural Psychosocial Organization Uganda. Over nine months, 2385 children sought mental health services, with CCDT implementation resulting in a significant increase in service use, particularly in the first month (20.91-fold increase). While service use declined slightly over time, CCDT zones maintained a higher rate of engagement, demonstrating the tool's potential for bridging the mental health service gap among children in low-resource settings when paired with accessible care.