A Study Evaluating the Efficacy and Safety of Guselkumab Administered Subcutaneously in Participants With Active Psoriatic Arthritis

Inclusion Criteria:

Have a diagnosis of Psoriatic Arthritis (PsA) for at least 6 months before the first administration of study agent and meet Classification criteria for Psoriatic Arthritis (CASPAR) at screening
Have active PsA as defined by: at least 5 swollen joints and at least 5 tender joints at screening and at baseline, and CRP greater than or equal to (>=) 0.6 milligram per deciLitre (mg/dL) at screening from the central laboratory
Have at least 1 of the PsA subsets: distal interphalangeal joint involvement, polyarticular arthritis with absence of rheumatoid nodules, arthritis mutilans, asymmetric peripheral arthritis, or spondylitis with peripheral arthritis (confirmation of sacroiliitis should be performed at the screening visit by a locally performed pelvic x-ray [single anterior-posterior view] unless a pelvic or SI joint x-ray or pelvic magnetic resonance imaging (MRI) has been previously performed. Results must be documented)
Have active plaque psoriasis, with at least one psoriatic plaque of >= 2 centimeter (cm) diameter or nail changes consistent with psoriasis or documented history of plaque psoriasis
Have active PsA despite previous non-biologic disease-modifying antirheumatic drug (DMARD), apremilast, and/or nonsteroidal anti-inflammatory drug (NSAID) therapy

Exclusion Criteria:

Has other inflammatory diseases that might confound the evaluations or benefit of guselkumab therapy, including but not limited to rheumatoid arthritis (RA), axial spondyloarthritis (this does not include a primary diagnosis of PsA with spondylitis), systemic lupus erythematosus, or Lyme disease
Has previously received any biologic treatment
Has ever received tofacitinib, baricitinib, filgotinib, peficitinib (ASP015K), decernotinib (VX-509), or any other Janus kinase (JAK) inhibitor
Has received any systemic immunosuppressants (eg, azathioprine, cyclosporine, 6 thioguanine, mercaptopurine, mycophenolate mofetil, hydroxyurea, tacrolimus) within 4 weeks of the first administration of study agent
Is currently receiving 2 or more non-biologic DMARDs (other than methotrexate [MTX], sulfasalazine [SSZ], Hydroxychloroquine [HCQ], leflunomide [LEF]) including, but not limited to chloroquine, gold preparations, and penicillamine within 4 weeks before the first administration of study agent
Has received apremilast within 4 weeks prior to the first administration of study agent