Psoriasis is a chronic inflammatory disease affecting 2% to 3% of the population in Western countries. Psoriasis is associated with limited quality of life, cardiovascular disease, and depression. The approval of injectable biological agents has revolutionized the management of moderate to severe psoriasis. Adalimumab is a human monoclonal antibody against tumor necrosis factor (TNF) alpha approved for moderate-to-severe plaque-type psoriasis and psoriatic arthritis (PsA). This systematic review summarizes the evidence concerning the efficacy, clinical effectiveness, safety, and cost-effectiveness of adalimumab in the treatment of psoriasis. Five randomized controlled trials demonstrated the efficacy of adalimumab in moderate-to-severe plaque-type psoriasis and PsA with PASI-75 response rates of 53% to 80% and ACR-20 response rates of 39% to 58% after 12 to 16 weeks of treatment. In clinical practice patients who have not responded to one TNF antagonist may respond to another TNF antagonist. Adalimumab has similar or better cost-effectiveness than other biologics, but is less efficient than methotrexate and cyclosporine. Adalimumab is generally well tolerated. Patients should be evaluated for active/latent tuberculosis, serious infections, and other contraindications prior to initiation of adalimumab therapy. Future studies should investigate the comparative efficacy of adalimumab and other biologic and prebiologic agents. Recently established registries will yield additional data on the effectiveness and long-term safety of adalimumab.