Objective: To evaluate the feasibility and acceptability of a school-based intervention for diverse children exposed to a range of traumatic events, and to examine its effectiveness in improving symptoms of posttraumatic stress, depression, and anxiety. Method: Participants were 74 schoolchildren (Grades 1-5) and their primary caregivers. All participating students endorsed clinically significant posttraumatic stress symptoms. School clinicians were trained to deliver Bounce Back, a 10-session cognitive-behavioral group intervention. Children were randomized to immediate or delayed (3-month waitlist) intervention. Parent- and child-report of posttraumatic stress and depression, and child report of anxiety symptoms, were assessed at baseline, 3 months, and 6 months. Results: Bounce Back was implemented with excellent clinician fidelity. Compared with children in the delayed condition, children who received Bounce Back immediately demonstrated significantly greater improvements in parent- and child-reported posttraumatic stress and child-reported anxiety symptoms over the 3-month intervention. Upon receipt of the intervention, the delayed intervention group demonstrated significant improvements in parent- and child-reported posttraumatic stress, depression, and anxiety symptoms. The immediate treatment group maintained or showed continued gains in all symptom domains over the 3-month follow-up period (6-month assessment). Conclusions: Findings support the feasibility, acceptability, and effectiveness of the Bounce Back intervention as delivered by school-based clinicians for children with traumatic stress. Implications are discussed.