Background: People with multiple sclerosis (MS) frequently report implementing dietary strategies as part of their personal wellness programs; however, little is known about the perceived themes of healthy behavior change in people with MS. Methods: Semistructured one-on-one interviews were conducted with 20 women with MS enrolled in 2 different restrictive dietary intervention studies and their 18 self-identified support persons consisting of partners and adult children. Interviews were transcribed, coded, categorized, and then grouped into summative themes. The frequency of issues being mentioned as facilitators of or barriers to diet adherence was evaluated to identify possible differences in perceived experiences between women with MS and their support persons during the studies. Results: Five qualitative themes were identified: (1) personal motivation, (2) diet components, (3) time, (4) support, and (5) resource access. Major facilitators of dietary adherence were positive support from support persons and study staff, access to resources, symptom improvement, and personal motivation. Major barriers included the novelty of the study diet, lack of cooking skills, no change in or worsening of symptoms, lack of diet knowledge, and food preferences and temptations. Symptom severity was more frequently reported as a barrier to study diet adherence among participants with secondary progressive MS. Conclusions: Methods to enhance personal motivation and ensure positive support from support persons and study staff may improve study diet adherence. Due to the unique challenges faced by people with MS, future studies should tailor interventions to their unique MS cohort to increase diet adherence.