We compared psychoeducation and problem solving (PEPS) therapy against usual treatment in a multisite randomized-controlled trial. The primary outcome was social functioning. We aimed to recruit 444 community-dwelling adults with personality disorder; however, safety concerns led to an early cessation of recruitment. A total of 154 people were randomized to PEPS and 152 to usual treatment. Follow-up at 72 weeks was completed for 68%. PEPS therapy was no more effective than usual treatment for improving social functioning (adjusted difference in mean Social Functioning Questionnaire scores = -0.73; 95% CI [-1.83, 0.38]; p = 0.19). PEPS therapy is not an effective treatment for improving social functioning of adults with personality disorder living in the community.