Objective: This study aimed to determine the number needed to treat (NNT), number needed to harm (NNH), and likelihood of being helped or harmed (LHH) in a post hoc analysis of the phase 3b FOCUS trial. Background: Fremanezumab, a humanized monoclonal antibody that selectively targets calcitonin gene–related peptide (CGRP), has demonstrated efficacy, tolerability, and safety in adults with episodic migraine (EM) or chronic migraine (CM), with documented previous inadequate response to two to four classes of migraine preventive medications. Methods: In the 12-week double-blind period of the FOCUS study, patients were randomized (1:1:1) to quarterly fremanezumab, monthly fremanezumab, or matched monthly placebo. NNT was based on responder analysis, defined as ≥50% reduction in monthly average number of migraine days at 12 weeks. NNH was based on discontinuations due to adverse events (AEs). Results: Among patients with CM (n = 509), response rates and discontinuation rates were 27% (45/169) and 0 for quarterly fremanezumab, 29% (50/173) and 2% (3/173) for monthly fremanezumab, and 8% (13/167) and <1% (1/167) for placebo, respectively. These results translated to NNTs of 5.3 and 4.7, NNHs of 1000 and 88, and LHHs of 188 and 19 for quarterly and monthly fremanezumab, respectively. Among patients with EM (n = 328), response rates were 47% (50/107) for quarterly fremanezumab, 43% (47/110) for monthly fremanezumab, and 10% (11/111) for placebo. Discontinuation rates were <1% (n = 1) in all three groups. These results translated to NNTs of 2.7 and 3.0, NNHs of 1000 and 1000, and LHHs of 368 and 328 for quarterly and monthly fremanezumab, respectively. Conclusions: The NNT, NNH, and LHH for quarterly and monthly fremanezumab compare favorably with those for traditional oral preventive medications, including topiramate, valproate, and propranolol.