Chronic migraine causes a serious labour loss and disability in the society and increases the risk of depression and anxiety by negatively affecting the quality of life. The purpose of this study was to investigate the effects of onabotulinumtoxinA (BoNT-A) treatment on efficacy before and after treatment in our cases with chronic migraine as well as on depression, anxiety and disability caused by migraine. According to the International Headache Classification (ICHD-III beta version), 60 adult patients who were diagnosed with chronic migraine were included in the study. A total of 155 IU BoNT-A treatment from 31 regions was administered in accordance with the protocol of PREEMPT study. Information about the characteristics of patients' headaches, background and family history, drugs they used was recorded. At the baseline and in the first and third month after the BoNT-A injection, VAS scores, the number of both headache days and attacks, the headache duration, the frequency of application to emergency services and the intake of both analgesics and triptans during attacks were evaluated. MIDAS, BDI and BAI were evaluated at the baseline and in the third month after the BoNT-A injection. BoNT-A injection provided a significant decrease in the number of days and severity of headaches, MIDAS disability scores and psychiatric complaints in cases with chronic migraine who did not respond to prophylactic treatments in the third month of the treatment.