BackgroundHeadache mobile health (mHealth) applications (apps) have gained popularity in use but there is little research into what people with migraine find important to track. This information is important for helping with adherence and determining meaningful data to patients. We conducted several clinical trials using a headache research app (RELAXaHEAD). The app contains a “notes” feature (a free‐text input section) where patients could record notes related to their headache.ObjectiveTo identify what patients view as important when tracking migraine/headaches within a headache tracking mHealth app.MethodsThis was a retrospective study where smartphone diary notes inputted by people with migraine were qualitatively analyzed; notes were extracted, a preliminary codebook was developed and used to code each note. Using grounded theory, themes and subthemes emerged.ResultsAbout 288 subjects in the trials used the notes function. There were 5364 total notes with an average of 18.6 ± 39.2 notes/user. The qualitative analysis yielded 759 unique codes and the emergence of 4 major themes. The first theme was “Utility in free‐text tracking of headache characteristics, medications, and sleep” which emerged as a space for users to elaborate on data that could have been inputted into other sections of the app. The second theme was “Monitoring coexisting conditions both related to and distinct from headache.” The third theme was “Personal records of behavioral therapy adherence,” which included a range of concepts from behavioral therapy session frequency/adherence to subjects’ thoughts or emotions regarding the behavioral therapy. The fourth theme was “Migraine trigger, prevention, and relief patterns deciphered through consistent data tracking.”ConclusionWe found that the majority of patients choose to expand on information beyond what can be inputted into specific icons in a headache app. Moreover, they want to be able to monitor not only headache‐related symptoms but symptoms they experience from other conditions. In addition to tracking their pharmacologic treatment, they may choose to track their nonpharmacologic, that is, behavioral therapy use, and they also use a smartphone diary app to assess what triggers versus relieves a migraine. While the RELAXaHEAD app was designed with features to extract data that would be useful to physicians and patients in treating migraine, our study results indicated that users also prefer a range of tracking capabilities that may or may not be useful to physicians but may be important for headache smartphone user engagement.