Background: This study examined the effects of a universal stress management program (Learn Young, Learn Fair) on stress, coping, anxiety and depression in fifth and sixth grade children. Methods: Fifty-two schools (1467 children) participated in a clustered randomized controlled trial. Data was collected in the fall of 2002, the spring of 2003, and the winter of 2004. Given the nested structure of the design mixed (multilevel) regression analyses were applied. Results: Positive effects were found for emotion-focused coping at posttest (p less than 0.01) and increased stress awareness at both time points. At posttest a decrease in problem solving was found (p less than 0.01). After correcting for mediation by stress awareness the results showed that the program significantly reduced stress symptoms (p = 0.05) and anxiety (p = 0.01) at posttest. Effect sizes varied from small to large. Conclusions: Universal prevention programs that address stress and coping in children are warranted given the high prevalence of stress in children and the relationship between stress, on the one hand, and health complaints and pathology, on the other. Such programs are expected to be particularly salient for children with an increased sensitivity to stress and inadequate coping styles (e.g., diathesis-stress model). The results indicate that the school-based program "Learn Young, Learn Fair" may be a valuable program for reducing stress in children.