The objective of this report is to perform a systematic review of the beneficial and harmful effects of ustekinumab 45 mg or 90 mg for the treatment of active psoriatic arthritis in adults, alone or in combination with methotrexate. Ustekinumab is a fully human IgG1 kappa monoclonal antibody that binds to the shared p40 subunit of interleukin (IL)-12 and IL-23 and is administered by subcutaneous injection of 45 mg or 90 mg at weeks 0 and 4 and every 12 weeks thereafter. Psoriatic arthritis (PsA) is a chronic inflammatory arthritis that can be associated with psoriasis, a skin disease. This seronegative form of arthritis can cause inflammation of the peripheral and axial joints, enthesitis, dactylitis, psoriatic skin lesions, and symptoms such as fatigue that are linked to systemic inflammation. Several classes of drugs are employed in the treatment of PsA, including nonsteroidal anti-inflammatory drugs (NSAIDs), disease-modifying antirheumatic drugs (DMARDs; i.e., methotrexate, sulfasalazine, and leflunomide), immunosuppressives (cyclosporine), and tumour necrosis factor (TNF) alpha inhibitors (i.e., etanercept, infliximab, golimumab, adalimumab, and certolizumab). Methotrexate remains the most frequently used DMARD despite limited evidence (two small controlled trials of inadequate power) that evaluated methotrexate for PsA.