Anxiety disorders are common in children and may signal risk of depression, social, or academic difficulties. This study evaluated the effects of a universal mental health promotion intervention delivered in primary schools. Three hundred and seventeen 9- to 10-year-olds were randomly allocated by class group to intervention conditions (psychologist-led or teacher-led), or a comparison condition. Coping and anxiety were measured pre- and post-intervention and at six-month follow-up. Significant anxiety reduction and improved coping were found post-intervention and at follow-up. There were no significant differences between the teacher- and psychologist-led intervention groups. Results indicated that a universal school programme delivered by teachers can have positive effects on anxiety and coping.