Background and Aims: A biosimilar version of infliximab [CT-P13/Remsima (R)] recently entered the European market. The clinical data on its use in inflammatory bowel disease [IBD] are sparse, especially on switching from the originator Remicade (R). In this study, we aimed to prospectively investigate the feasibility, safety and immunogenicity of switching from Remicade to Remsima in a real-life IBD population. Methods: All adult patients who were treated with Remicade in the Department of Gastroenterology at Oslo University Hospital were switched to Remsima. The follow-up lasted for 6 months. In addition, a retrospective registration was performed with a start time of 6 months before switching drugs. The primary endpoints were [i] the proportion of patients remaining on medication 6 months after switching and [ii] adverse events during the 6 months after switching. The secondary endpoints included [i] disease activity scores [Harvey-Bradshaw Index and Partial Mayo Score], C-reactive protein, haemoglobin, faecal calprotectin, infliximab dose and interval, and p-infliximab and [ii] the development of antidrug antibodies. Results: In total, 143 IBD patients were switched, 99 with Crohn's disease and 44 with ulcerative colitis. The large majority [97%] remained on the medication throughout follow-up. A low number of adverse events were observed. No change in disease activity, C-reactive protein, haemoglobin, faecal calprotectin, infliximab dose and interval or p-infliximab was detected. Three patients developed new detectable antidrug antibodies. Conclusions: Switching from Remicade to Remsima was feasible and with few adverse events, including very limited antidrug antibody formation and loss of response.