This study investigated the effectiveness of a social and emotional learning (SEL) group to enhance first-grade students' school adjustment. A seven-session intervention program was conducted by two group leaders and included training in social and emotional skills. Pre- and post- and follow-up assessment data were collected from a total of 114 first-grade Greek students and their teachers. Children attending the intervention group (n = 56) were found to exhibit better social skills and prosocial behavior, as well as less aggressive and disruptive behavior, according to teacher reports, than children in the (non-intervention) control group (n = 58). However, no group differences on children's self-reported school liking and avoidance, as well as on feelings of loneliness and social dissatisfaction, were found. Theoretical and practical implications of the finding are briefly discussed.