Limited data are available on health care resource utilization (HCRU) and health care costs of calcitonin gene-related peptide monoclonal antibodies (CGRP mAbs) for preventive treatment of migraine. To compare all-cause and migraine-related HCRU and direct health care costs in patients with migraine initiating CGRP mAbs, galcanezumab (GMB), vs standard-of-care (SOC) preventive treatments in the United States. This retrospective observational study used insurance claims data collected from IBM MarketScan Research Databases. Adults (aged ≥ 18 years) with 1 or more claims for CGRP mAb (GMB, erenumab, or fremanezumab) or SOC preventive treatment between May 1, 2018, and June 30, 2019, were included. The date of earliest migraine treatment claim during this period was the index date. Annual all-cause and migraine-related HCRU included inpatient visits, emergency department visits, and acute and preventive migraine medication fills. After matching, HCRU and costs at 6- and 12-month follow-up in CGRP mAb, specifically GMB, vs SOC cohorts were analyzed using paired t-test and chi-square test. In the 12-month follow-up study, 4,528 patients using CGRP mAb (GMB, n = 426) and 10,897 patients using SOC were included. After matching, 3,082 pairs were identified in the CGRP mAb and SOC cohorts and 421 pairs in the GMB and SOC cohorts. After matching, all variables were well balanced across cohorts. At 12-month follow-up, the percentage decrease in acute and preventive migraine medication fills was significantly greater in the CGRP mAb (acute: -1.5% vs -0.2%, < 0.001; preventive: -1.1% vs 3.8, < 0.001) and GMB cohorts (acute: -1.5% vs -0.2%, = 0.002; preventive: -1.8 vs 3.0, < 0.001) compared with the SOC cohort. At follow-up, compared with the SOC cohort, the mean change of annual all-cause total costs was significantly higher in both the CGRP mAb ($6,043 vs $1,323, < 0.001) and GMB cohorts ($8,398 vs $68, < 0.001), and the mean change of annual migraine-related total costs was significantly higher in both the CGRP mAb ($3,416 vs $976, < 0.001) and GMB cohorts ($4,334 vs $1,245, < 0.001). Significant cost savings in mean acute and preventive migraine prescription costs occurred in both the CGRP mAb (acute: -$358 vs -$80, < 0.001; preventive: -$298 vs $1,376, < 0.001) and GMB cohorts (acute: -$280 vs -$36, = 0.034; preventive: -$374 vs $1,537, < 0.001) compared with the SOC cohort. Although treatment with CGRP mAbs and GMB increase total costs, they may lead to significantly greater cost savings in outpatient acute and preventive migraine medication costs vs SOC. Further studies assessing indirect health care costs are important to understand additional cost savings with CGRP mAbs. Drs Varnado, Ye, and Schuh are employees and stockholders of Eli Lilly and Company. Dr Wenzel is a former employee of Eli Lilly and Company. Dr Manjelievskaia is an employee of IBM Watson Health. Ms Perry is a former employee of IBM Watson Health. This study was sponsored by Eli Lilly and Company. IBM Watson Health received funding for this study from Eli Lilly and Company. Independent analyses were conducted by IBM Watson Health. Eli Lilly and Company and IBM Watson Health collaborated on designing the study and interpreting results.