In patients with migraine, depression is associated with poorer medical prognosis, decreased quality of life, and increased risk of suicidality and disability; yet, behavioral interventions have rarely been investigated. The current study compared the efficacy of two 1-day (5- to 6-h) interventions for co-occurring migraine and depression: (1) acceptance and commitment therapy plus migraine education (ACT-ED), and (2) support plus migraine education (S-ED). One hundred and thirty-six patients with comorbid depression and migraine were randomized to a treatment. One hundred and three (76%) completed the ACT-ED (N = 56) or S-ED (N = 47) workshop. Primary outcomes were depression diagnosis and symptoms. Secondary outcomes were anxiety symptoms, headache-related disability and general functioning, and quality of life. Assessments were completed at baseline and 3 and 6 months following the workshop. At the 6-month follow-up, on categorical outcomes, a significantly greater number of people in the ACT-ED condition no longer met criteria for a major depressive episode and exhibited a > 50% drop in symptoms on the Hamilton Rating Scale of Depression. Similarly, though, weaker results were found when examining depressive symptoms dimensionally. On secondary outcomes, people in the ACT-ED condition exhibited significantly greater improvements in anxiety, headache-related disability, and quality of social relationships, compared to S-ED, No differences between groups were observed in general functioning. A 1-day (5- to 6-h) ACT workshop can deliver substantial and lasting benefits to depressed migraineurs, over and above those provided by group support and education. This approach is an attractive alternative to weekly psychotherapy. Clinicaltrials.gov # NCT02108678.