The aim of this study was to investigate the validity of the ID Migraine (TM) test in neurology outpatient clinics (NOCs), regardless of their presenting complaints. Patients admitted to 41 NOCs were screened. Eligible subjects (n = 3682) were evaluated by a neurologist for headache diagnosis according to the International Headache Society criteria and asked the 3-item screening questions of the ID Migraine (TM) test. Of 3682 patients, 917 (24.9%) were diagnosed as migraine, whereas 1171 (31.8%) were ID Migraine (TM) test positive. The sensitivity of the ID Migraine (TM) test for neurologist's diagnosis of migraine was 91.8%, specificity was 63.4%, positive predictive value was 71.9% and negative predictive value was 88.4%. The ID Migraine (TM) test is easy to use and a practical test that could alert the neurologist to diagnose patients having other complaints. This test would help to increase the diagnosis and treatment rate of undiagnosed migraine patients in NOCs.