Background In multiple sclerosis (MS), the measure of the loss of autonomy appears to be particularly relevant to provide adapted and personalized responses to improve the quality of care in routine clinical practice. In this context, this research aimed to develop a new patient-reported outcome measure (PROM) evaluating MS patients’ autonomy, in order to provide an easy-to-use tool in the context of the relations between healthcare professionals and patients with MS, and to be used in future clinical trials for treatment assessment. Methods This research was conducted in two consecutive stages. First, a preliminary questionnaire was generated using an innovative sociological approach for MS (after literature review, patient interviews, experts’ opinion, and patient focus groups). This questionnaire was then completed by patients with MS, before the reduction of the scale while maintaining relevant information, using a principal component analysis. The internal consistency reliability was assessed using the Cronbach's alpha coefficient. The external validity was evaluated using an analysis of variance to estimate the relation between the reduced questionnaire dimension scores and disease severity classes assessed by the SymptoMScreen questionnaire. Results The first qualitative step of the research led to provide a definition of disease-related autonomy as perceived by patients (to be able to carry out the roles the patient thinks the most important whether or not he/she receives assistance) as well as an associated taxonomy. On this basis, a preliminary questionnaire of 131 items grouped into 13 social dimensions was generated (seven dimensions with 63 questions concerning all the patients, and six dimensions with 68 questions concerning specific patients). This questionnaire was completed on a web platform by 653 analyzable patients with MS. Their main characteristics were as follows: female patients: 83.6 %, mean age at MS diagnosis: 34.8 ± 10.5 years, age ≥40 years at data collection: 68.1 %, MS duration ≥5 years: 68.4 %, severe MS (SymptoMScreen score ≥30): 36.8 %. On the basis on completed 131-item questionnaires, it was reduced in a 36-item short form of 10 social dimensions (five dimensions with 19 questions concerning all the patients, and five dimensions with 17 questions concerning specific patients). The internal consistency of the final questionnaire was good for all the dimensions, as the Cronbach's alpha coefficient ranged from 0.77 to 0.85 depending on dimensions. The construct validity of the questionnaire was also confirmed. Conclusion Our research allowed to build the first PROM designed to evaluate the autonomy of patients suffering from MS: the Multiple Sclerosis Autonomy Scale (MSAS). A confirmatory study, conducted in patients with MS using this validated questionnaire, is currently conducted.