<b><i>Objective:</i></b> Complementary therapies have been increasingly used for the prevention and treatment of migraine so that there is a need for studies in this setting. This study sought to determine the effects of basil essential oil on the severity and frequency of migraine attack headaches. <b><i>Methods:</i></b> A triple-blind clinical trial study was performed on 144 patients diagnosed with migraine. Patients were randomly allocated by a stratified method to four groups of 36 titled basil essential oil 2, 4, 6%, and placebo groups. Medications were used topically every 8 h for 3 successive months. In addition, each individual received 325 mg of acetaminophen every 12 h. The severity and frequency of migraine attacks were measured prior to the study, at weeks 2, 4, 8, and 12. The visual analog scale was used to measure pain intensity. The marginal model and generalized estimation equations were used to compare changes in the intensity and frequency of pain over time. <b><i>Results:</i></b> The interaction of the dose and time factors was significant on both pain intensity (<i>p</i> &#x3c; 0.001) and frequency of attack (<i>p</i> &#x3c; 0.001). The odds ratio of higher pain intensity and rate ratio of higher frequency of attack in the intervention groups compared to the placebo group were decreased over the study time. <b><i>Conclusion:</i></b> Time lapse and higher doses of basil essential oil would reduce both the intensity and frequency of migraine attacks.