Certolizumab pegol is a humanized Fab' fragment monoclonal antibody to tumor necrosis factor alpha (TNF-alpha). PEGylation increases its half-life, and it is administered subcutaneously to treat immune-mediated inflammatory diseases such as Crohn's disease and rheumatoid arthritis. Certolizumab pegol improves quality of life and reduces clinical disease activity. Inflammatory markers such as C-reactive protein (CRP) also decrease after administration of certolizumab pegol. The dose for induction of remission is 400 mg subcutaneously at weeks 0, 2 and 4. The dose for maintenance of remission is 400 mg sc given every four weeks. The safety profile is comparable with other anti-TNF agents, and the major adverse events are related to infections. This article reviews the published data regarding the efficacy and safety of certolizumab pegol.