Psoriasis is a complex, multigenic immune/inflammatory-mediated disorder that variably affects the skin, nails, and joints. In September 2009, ustekinumab (Stelara®), a monoclonal antibody that targets interleukin 12 (IL-12) and 23 (IL-23), was approved in the United States for treatment of moderate-to-severe plaque psoriasis. The drug's mechanism of action is derived from extensive immunologic and genomic research identifying IL-12 and IL-23 of the Th1 and Th17 inflammatory pathways, respectively, as key mediators of psoriasis. Ustekinumab is a completely human monoclonal antibody to the shared p40 subunit of IL-12 and IL-23. The drug has demonstrated efficacy, short-term safety, and convenience of use in the treatment of plaque psoriasis and psoriatic arthritis. Though long-term safety concerns remain, ustekinumab adds to the current treatment armamentarium and holds promise to improve quality of life. This is a concise and current review of ustekinumab in the treatment of plaque psoriasis and psoriatic arthritis, with focus on data from the seven published clinical trials.