OBJECTIVES: Biosimilar infliximab (Inflectra®) has been approved by the European Medicines Agency for the treatment of severe active ankylosing spondylitis (AS) in adult patients since 2013. Currently in most European countries, the price of biosimilars is considerably lower compared to the reference product. We aim to compare cost-effectiveness of adalimumab, certolizumab pegol, etanercept, golimumab, infliximab and biosimilar infliximab for the treatment of AS in nine European countries (Belgium, France, Germany, Hungary, Italy, the Netherlands, Spain, Sweden and the UK). METHODS: A probabilistic Markov model was developed to compare the cost-effectiveness of selected biological treatment sequences to standard care or to other biological sequences in AS patients who have responded inadequately to conventional therapy. Model outcomes were based on the reduction in Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) score. The model included costs of drugs, monitoring, administration and hospitalisation from third-party payer perspective. A five-year time horizon was adopted, and both costs and benefits were discounted at country-specific discount rates. RESULTS: The incremental cost-utility ratios (ICUR) of biosimilar infliximab versus standard care were as follows: €34,977/QALY (Belgium), €41,948/QALY (France), €55,309/QALY (Germany), €28,191/QALY (Hungary), €33,454/QALY (Italy), €34,437/QALY (the Netherlands), €37,361/QALY (Spain), €51,431/QALY (Sweden) and €47,880/QALY (the UK). Compared to standard care, the originator infliximab was dominated by the biosimilar infliximab in all countries. The inclusion of additional biologicals to the treatment sequence resulted in higher cost-utility ratios. ICURs of biosimilar infliximab-etanercept-adalimumab sequence ranged from €40,672/QALY to €79,678/QALY and between €42,329/QALY and €84,412/QALY for the biosimilar infliximab-certolizumab pegol-golimumab sequence. The results were the most sensitive to changes in the perspective of the analysis, utility weights and time horizon (10-year). CONCLUSIONS: Biosimilar infliximab is a cost-effective alternative to the originator product for the treatment of adults with severe active AS that may increase the affordability of, and thus the access to biological treatments in Europe.