Migraine is a common neurological disorder globally. Migraines, with or without aura, are episodic and recurring with symptom-free periods. Frequent and prolonged attacks can lead to chronic migraine. This pilot randomized controlled trial (RCT) aimed to evaluate feasibility of therapist-guided, acceptance-based internet cognitive behavioral therapy (iCBT) as an adjunct to standard medical care for migraine patients in Swedish primary healthcare settings using a mixed methods approach. Participants (treatment n = 15, control n = 14) underwent qualitative and quantitative assessments to evaluate feasibility, acceptance, and initial treatment effects. Interviews with participants (n = 7) indicate that most participants had struggled with migraines for decades and expressed dissatisfaction with the limited medical care. They found the flexible, digital format particularly helpful, praising its accessibility and structured learning. While they appreciated the comprehensive content, some faced challenges with the psychological language and the program pace. Post-treatment, participants reported emotional and behavioral changes, and better migraine management. Seventy-two percent of the 29 participants completed both baseline and 3-month follow-up measures. On average, participants completed 7.7 modules, with 60% completing all 10 modules. Promising effect size indicated a reduction in migraine days during the three-month follow-up. Both qualitative and quantitative data support the feasibility and acceptability of the intervention in primary care settings.