ObjectiveTo understand the effectiveness of ustekinumab in treating Crohn’s disease (CD) in a UK real-world setting.DesignRetrospective cohort study using prospectively maintained clinical records.SettingSingle UK inflammatory bowel disease centre.PatientsAdult patients with an established diagnosis of CD prescribed ustekinumab outside of clinical trials at University Hospital Southampton (UHS).InterventionsUstekinumab, a monoclonal antibody to the shared p40 subunit of interleukin (IL) 12 and IL-23 as part of routine clinical care.Main outcome measuresEffectiveness as measured by an improvement in physician’s global assessment, drug persistence and improvement in biomarkers (C-reactive protein (CRP), albumin and calprotectin).Results84 patients were included, 72 had a postinduction review and 49 had 1-year data. At postinduction clinical review, clinical response occurred in 53% of patients and clinical remission occurred in 8%. For patients on ustekinumab at 1 year, clinical response occurred in 71% and remission in 14%. Adverse events included four patients with infections requiring admission, one drug-related rash, five CD surgeries and two CD exacerbations.ConclusionsUstekinumab was well tolerated in a complex UK CD population and demonstrated benefit to patients in terms of clinical response and improvement of biomarkers and with some patients attaining clinical remission. No unexpected safety signals were seen.