Introduction: Intravenous immunoglobulin (IVIG) has been shown to be effective in treating steroid-refractory dermatomyositis (DM). There remains no evidence of its cost-effectiveness in Thailand. Objective: Our objective was to estimate the cost utility of IVIG as a second-line therapy in steroid-refractory DM in Thailand. Methods: A Markov model was developed to estimate the relevant costs and health benefits for IVIG plus corticosteroids in comparison with immunosuppressant plus corticosteroids in steroid-refractory DM from a societal perspective over a patient?s lifetime. The effectiveness and utility parameters were obtained from clinical literature, meta-analyses, medical record reviews, and patient interviews, whereas cost data were obtained from an electronic hospital database and patient interviews. Costs are presented in US, year 2012 values. All future costs and outcomes were discounted at a rate of 3 per annum. One-way and probabilistic sensitivity analyses were also performed. Results: Over a lifetime horizon, the model estimated treatment under IVIG plus corticosteroids to be cost saving compared with immunosuppressant plus corticosteroids, where the saving of costs and incremental quality-adjusted life-years (QALYs) were US4738.92 and 1.96 QALYs, respectively. Sensitivity analyses revealed that probability of response of immunosuppressant plus corticosteroids was the most influential parameter on incremental QALYs and costs. At a societal willingness-to-pay threshold in Thailand of US5148 per QALY gained, the probability of IVIG being cost effective was 97.6 . Conclusions: The use of IVIG plus corticosteroids is cost saving compared with treatment with immunosuppressant plus corticosteroids in Thai patients with steroid-refractory DM. Policy makers should consider using our findings in their decision-making process for adding IVIG to corticosteroids as the second-line therapy for steroid-refractory DM patients.