ABSTRACT Objective: To compare the cost of adverse events (AEs) associated with preventive treatment of migraine with fremanezumab, versus erenumab, galcanezumab, and onabotulinumtoxinA. Methods: A probabilistic modeling analysis was performed, using second-order Monte Carlo simulations, with 1,000 simulations, in patients with at least 4 days of migraine per month, from the perspective of the National Health System and a time horizon of 12 weeks. The frequency of AEs described in the clinical trials was analyzed with 12 weeks of treatment. Unit costs (€) of management of AEs were obtained from public health prices, expert panels, and published Spanish studies. Results: Fremanezumab would generate average savings of -€469 (95% CI -€303; -€674) versus erenumab, -€268 (95% CI -€171; -€391) versus galcanezumab, -€1,100 (95% CI -€704; -€1,608) or -€1,295 (95% CI -€835; -€1,893) versus onabotulinumtoxinA using real-life or clinical trial data, respectively. Conclusions: The different safety profile of treatment with fremanezumab, compared to erenumab, galcanezumab, and onabotulinumtoxinA, would generate savings in health-care resources in all the scenarios considered.