Abstract Introduction Long-term (1-year) fremanezumab treatment proved to be effective, safe, and well tolerated in individuals with migraine and 3 treatment failures and various comorbidities. Methods A 48-week, prospective, multicenter (n = 26), cohort study assessed fremanezumab’s effectiveness, safety, and tolerability in consecutive adults with HFEM or CM with > 3 treatment failures. Primary endpoint was variation from baseline in monthly migraine days (MMD) in HFEM and monthly headache days (MHD) in CM at weeks 45–48. Secondary endpoints were changes in monthly analgesic medications, Numerical Rating Scale (NRS), Headache Impact Test (HIT-6), and the Migraine Disability Assessment Scale (MIDAS) scores and ≥ 50%, ≥ 75%, and 100% responder rates. Results Of 533 participants who had received ≥ 1 fremanezumab dose, 130 were treated for ≥ 48 weeks and considered for effectiveness analysis. No participant missed any treatment dosage every other consecutive month during the 12-month period. Primary endpoint: fremanezumab significantly (p 3) therapeutic failures, even in the presence of concomitant medication overuse, psychiatric comorbidities, or both. The effectiveness-to-tolerability ratio appears to be better in RWE than in RCTs.