Objectives: To evaluate the efficacy of guselkumab for the treatment of active PsA utilizing composite indices. Methods: Data were pooled from the phase 3 DISCOVER-1 (n = 381) and DISCOVER-2 (n = 739) studies. In both studies, patients were randomized 1:1:1 to subcutaneous guselkumab 100 mg every 4 weeks (Q4W); guselkumab 100 mg at week 0, week 4, then Q8W; or placebo Q4W with crossover to guselkumab 100 mg Q4W at week 24. Composite indices used to assess efficacy through week 52 included Disease Activity Index for Psoriatic Arthritis (DAPSA), Psoriatic Arthritis Disease Activity Score (PASDAS), minimal disease activity (MDA), and very low disease activity (VLDA). Through week 24, treatment failure rules were applied. Through week 52, non-responder imputation was used for missing data. Results: Greater proportions of guselkumab- than placebo-treated patients achieved DAPSA low disease activity (LDA) and remission, PASDAS LDA and VLDA, MDA, and VLDA at week 24 vs placebo (all unadjusted P < 0.05). At week 52, in the guselkumab Q4W and Q8W groups, respectively, response rates were as follows: DAPSA LDA, 54.2% and 52.5%; DAPSA remission, 18.2% and 17.6%; PASDAS LDA, 45.3% and 41.9%; PASDAS VLDA, 16.9% and 19.5%; MDA, 35.9% and 30.7%; and VLDA, 13.1% and 14.4%. In the placebo-crossover-to-guselkumab group, response rates for all composite indices increased after patients switched to guselkumab, from week 24 through week 52. Conclusion: Treatment with guselkumab provided robust and sustained benefits across multiple PsA domains through 1 year, indicating that guselkumab is an effective therapy for the diverse manifestations of PsA. Trial registration: NCT03162796; NCT03158285