Calcitonin gene–related peptide monoclonal antibodies, a targeted treatment for migraine prevention, are effective and safe. To explore the practicality and tolerability of erenumab in Thailand, a retrospective study, preliminary report was conducted on patients with migraine at the Chulalongkorn Comprehensive Headache Center, King Chulalongkorn Memorial Hospital. All patients with migraine aged 18 years or older and treated with erenumab were included. Data was gathered from standardized patient–record forms, electronic medical records, headache diaries, and the Thai-version of the Migraine–Specific Quality of Life questionnaire version 2.1 and the Migraine Disability Assessment questionnaire. Of the 16 patients, 12 completed the first three-month injections. Most of them failed at least three preventive medications. Three patients with high–frequency episodic migraine had a 33% achievement of a 50% responder rate but no consistent response, and nine patients with chronic migraine and chronic migraine with medication–overuse headache had 67–100% and 33–75% achievement of a 30% and 50% responder rate, respectively. Three patients with no or fluctuating responses increased to erenumab 140 mg with responsiveness. The majority of patients with medication–overuse headaches had no detoxification procedures in place, and they all reverted to non-medication overuse. Patients were tolerable to the erenumab, which is practical and effective for migraine prevention. A dose of 140 mg should be started in patients who have resisted conventional preventive treatments. A detoxification procedure might not be necessary, but needs more research as well as an optimal duration for continuation of this class of medicine.