This study tested the efficacy of a generic social skills intervention, Social Skills GRoup INtervention (S.S.GRIN), for children experiencing peer dislike, bullying, or social anxiety. Third-grade children were randomly assigned to treatment (n = 187) or no-treatment control (CO; n = 194) groups. Examination of the direction and magnitude of change in functioning revealed that S.S.GRIN increased peer liking, enhanced self-esteem and self-efficacy, and decreased social anxiety compared to controls. S.S.GRIN was equally efficacious for all subtypes of peer problems targeted. Particular benefits were found for aggressive children who showed greater declines in aggression and bullying behavior and fewer antisocial affiliations than aggressive control participants. Discussion focuses on the benefits of heterogeneous versus homogeneous groups of participants and the potential value of utilizing generic social skills training protocols.