A Study of Guselkumab in Participants With Active Psoriatic Arthritis

Inclusion Criteria:

• Have active psoriatic arthritis (PsA) despite previous non-biologicdisease-modifying antirheumatic drug (DMARD), apremilast, and/or nonsteroidalanti-inflammatory drug (NSAID) therapy

• Have a diagnosis of PsA for at least 6 months before the first administration ofstudy agent and meet Classification criteria for Psoriatic Arthritis (CASPAR) atscreening

• Have active PsA as defined by: at least 3 swollen joints and 3 tender joints atscreening and at baseline; and C-reactive protein (CRP) greater than or equal to (>=) 0.3 milligrams per deciliter (mg/dL) at screening from the central laboratory

• Have >= 2 joints with erosions on baseline radiographs of the hands and feet asdetermined by central read

• Have at least one of the following PsA subsets: distal interphalangeal jointinvolvement, polyarticular arthritis with absence of rheumatoid nodules, arthritismutilans, asymmetric peripheral arthritis, or spondylitis with peripheral arthritis

• Have active plaque psoriasis, with at least one psoriatic plaque of >= 2 centimeter (cm) diameter or nail changes consistent with psoriasis

Exclusion Criteria:

• Has known allergies, hypersensitivity, or intolerance to study intervention or itsexcipients

• Has other inflammatory diseases that might confound the evaluations of benefit ofguselkumab therapy, including but not limited to rheumatoid arthritis (RA), axialspondyloarthritis (AS)/non-radiographic axial spondyloarthritis (nr-axSpA), systemiclupus erythematosus, or Lyme disease

• Has previously received any biologic treatment

• Has ever received tofacitinib, baricitinib, filgotinib, peficitinib, decernotinib,upadacitinib or any other Janus kinase (JAK) inhibitor

• Has received any systemic immunosuppressants (example, azathioprine, cyclosporine, 6thioguanine, mercaptopurine, mycophenolate mofetil, hydroxyurea, tacrolimus) within 4 weeks of the first administration of study intervention