Objectives(1) To explore experiences of fatigued persons with multiple sclerosis (pwMS) with a new multimodal agility-based exercise training (MAT) framework and (2) to investigate the demands of the Rehabilitation, Fatigue, and Exercise (ReFEx) study protocol, which compares high-frequency MAT and ‘traditional’ strength and endurance training (SET) to identify possible adaptations for a powered randomised controlled trial (RCT).DesignA qualitative interview study nested within a feasibility RCT, comparing MAT and SET.SettingNeurological inpatient rehabilitation centre in Germany.ParticipantsTwenty-two pwMS were recruited for the feasibility study. Six were selected from MAT and SET, respectively, for semistructured face-to-face interviews prior to discharge, following a purposive sampling strategy. Participants had low physical disability but were at least moderately fatigued.InterventionsDuring inpatient rehabilitation (4–6 weeks) MAT participants attended group-based and manual-based MAT sessions in the gym (5×/week, 30 min) and the pool (3×/week, 30 min). SET participants exercised individually on a cycle ergometer (5×/week, 22 min) and on strength training machines (3×/week, 30 min).ResultsThree key categories emerged from the interviews: (1)facilitatorsregarding MAT were variety and playfulness, group setting and challenging exercises.Barriersregarding MAT were feeling overburdened, feeling pressured in the group setting and the wish to perform ‘traditional’ strength training (not part of MAT). (2) MATbenefitswere of physical and psychological nature, with improved balance stated the most. (3)Demandsdescribed the perceived exertion during MAT and SET, reflecting that there is no accumulation of fatigue during the intervention.ConclusionsMAT is appreciated by pwMS and includes facilitators less attainable with ‘traditional’ SET. Evaluation of MAT in a powered RCT is indicated, if rest breaks postsession, and screening for negative self-evaluation and social comparison are considered. Future (qualitative) research should investigate the important factors of inpatient rehabilitation contributing to fatigue reduction in pwMS.Trial registration numberDRKS00023943; German Clinical Trials Register.