Clinical trial EMR 62202-006 demonstrates prolonged median locoregional control (24.4 vs. 14.9 months), progression-free survival (17.1 vs. 12.4 months) and overall survival (49.0 vs. 29.3 months) for patients who receive cetuximab added to the comparator radiotherapy for locally advanced squamous cell carcinoma of the head and neck (LA SCCHN). In the Netherlands, hospitals receive reimbursement for cetuximab conditional on cost-effectiveness in daily practice. To estimate the real-world incremental cost per quality adjusted life-year (QALY) gained for radiotherapy + cetuximab over radiotherapy alone in first line treatment of LA SCCHN, a Markov model is constructed with health states “alive without progression”, “alive following progression” and “death”. Transition probabilities per month are estimated from clinical trial data and retrospectively collected real-world data from two Dutch head and neck cancer treatment centres (2007–2010, n = 141). 5-year, 10-year and lifetime horizons are used, without and with discounting (4 % costs, 1.5 % effects) to calculate incremental cost-effectiveness ratios. Two scenarios explore different assumptions on prognosis of real-world versus trial patients. Adding cetuximab to radiotherapy results in increased costs and health gains in both scenarios and across each of the time horizons. Incremental costs per QALY gained range between €14,624 and €38,543 in the base-case. For a willingness to pay of €80,000 per QALY, the acceptability curves for the different scenarios show probabilities between 0.76 and 0.87 of radiotherapy + cetuximab being cost-effective compared to radiotherapy alone. Current results show the combined treatment of radiotherapy + cetuximab to be a cost-effective treatment option for patients with LA SCCHN.@en