This study was designed to assess the effectiveness of a multifocused (child-, teacher- and parent-focused) prevention program for Romanian preschoolers, targeting social–emotional competence development, as well as reduction of behavior problems. Fourteen classrooms were randomly assigned to the intervention and control conditions. Subsequent hierarchical linear analyses indicated that intervention-group children performed better on experimental tasks measuring emotion knowledge and social problem-solving strategies, and received higher assessments by their teachers and parents on measures of social–emotional competencies and externalizing problems. These results indicate that a prevention program combining intervention strategies for both high- and low-risk children is effective across a wide range of adaptive and maladaptive behaviors. Moreover, a short four-session parent group training employed to attract parent participation elicited an acceptable overall attendance rate (54%), indicating the sustainability of parent intervention in the context of community-based interventions.