Introduction The purpose of the present study is to compare the effect of the physiotherapy to onabolulinumtoxin-A, and their combination, in relation to cervical and headache parameters in patients with chronic migraine. Methods This is an observational cohort study conducted by a headache center and a physiotherapy degree course on 30 patients with chronic migraine. The patients were distributed in three groups of treatments for three months: onabolulinumtoxin-A only, physiotherapy only, and onabolulinumtoxin-A plus physiotherapy. The patients were evaluated, before and after each treatment, using the following: the postural assessment software SAPO for the forward head posture; the CROM goniometer for the cervical range of motion; the Migraine Disability Assessment Score for headache parameters. Results After 3 months of each treatment, the scores obtained for the headache-related disability and the frequency of migraine decreased significantly for all groups, but the pain intensity scores changed significantly only in the onabolulinumtoxin-A (p = 0.01) and in the onabolulinumtoxin-A plus physiotherapy groups (p = 0.007). On the other hand, the forward head posture was reduced significantly in the physiotherapy (p = 0.002) and in the onabolulinumtoxin-A plus physiotherapy groups (p = 0.003). The cervical range of motion increased significantly in certain directions in the physiotherapy group and in the onabolulinumtoxin-A plus physiotherapy groups. Conclusions The physiotherapy improved the cervical parameters. The onabolulinumtoxin-A decreased pain intensity. As a consequence, it can be said that the combined treatment was more useful than a mono-therapy alone. From our results, it can be concluded that onabolulinumtoxin-A plus physiotherapy could be a good option in the management of chronic migraine.