Biological agents are effective in ulcerative colitis (UC). Currently, 3 anti-TNF agents (infliximab, adalimumab, and golimumab) and 1 anti-integrin agent (vedolizumab) are approved for the treatment of UC. The mechanism of action of biologic agents can also give rise to several side effects, some even serious. It remains uncertain to what extent biologic treatments may be associated with an increased rate of infections, malignancies and other adverse events Areas covered: Our aim is to review the relevant data available in the literature and briefly summarize the safety profile of biological therapy in UC. We performed a literature search using the OVID, MEDLINE, PUBMED and EMBASE databases. Also other relevant sources of safety data were also used. Expert opinion: All biological agents currently used in UC are relatively safe. Accurate prevention measures and screening prior to start such therapies, and regular surveillance programs are strongly recommend to minimize any risk of infections, malignancy and other adverse events related to the use of monoclonal antibodies in UC patients.