INTRODUCTION: Although hand temperature and electromyograph biofeedback have evidence for migraine prevention, to date, no study has evaluated heartrate variability (HRV) biofeedback for migraine. METHODS: 2-arm randomized trial comparing an 8-week app-based HRV biofeedback (HeartMath) to waitlist control. Feasibility/acceptability outcomes included number and duration of sessions, satisfaction, barriers and adverse events. Primary clinical outcome was Migraine-Specific Quality of Life Questionnaire (MSQv2). RESULTS: There were 52 participants (26/arm). On average, participants randomized to the Hearthmath group completed 29 sessions (SD = 29, range: 2-86) with an average length of 6:43 min over 36 days (SD = 27, range: 0, 88) before discontinuing. 9/29 reported technology barriers. 43% said that they were likely to recommend Heartmath to others. Average MSQv2 decreases were not significant between the Heartmath and waitlist control (estimate = 0.3, 95% CI = -3.1 - 3.6). High users of Heartmath reported a reduction in MSQv2 at day 30 (-12.3 points, p = 0.010) while low users did not (p = 0.765). DISCUSSION: App-based HRV biofeedback was feasible and acceptable on a time-limited basis for people with migraine. Changes in the primary clinical outcome did not differ between biofeedback and control; however, high users of the app reported more benefit than low users.