AIM: Preschoolers with behavioural difficulties, both at clinical and sub-clinical levels, are at higher risk for several negative outcomes. The current paper reports the results from a randomized clinical trial evaluating an adaptation of the Coping Power for preschool-aged children. In the present study, Coping Power is adapted as a universal prevention intervention, in which teachers deliver a curriculum that is designed to improve children’s social competence and reduce problem behaviours. METHODS: Ten nursery school classes (164 children, mean age 54.40 months) from two Italian schools were randomly assigned to Coping Power or to the control group, which received the standard academic curriculum provided in Italian nursery schools. Teachers in the five intervention classes implemented weekly lessons and extension activities over a 6-month period. Teacher and parent reports of child behaviour assessments were collected at the beginning and end of the school year. At each assessment period, teachers completed the Strengths and Difficulties Questionnaire. RESULTS: The findings suggest that after exposure to Coping Power, intervention children showed lower levels of behavioural difficulties, rated both by parents and teachers. CONCLUSIONS: The results of this study are promising and can be interpreted as providing initial support for the efficacy of the preschool version of Coping Power.