Purpose: To identify the most pressing needs for community resources to support physical activity participation, determinants of perceived need, and barriers to co-participation in physical activity among people with multiple sclerosis (MS) who have moderate-to-severe disability and the family caregivers providing assistance to such individuals. Methods: Seventy-eight people with MS and 46 family caregivers participated in this cross-sectional survey study, guided by the Concerns Report Methodology. Results: The results show differences between groups in rankings for some need items. However, three need items were prioritized by both people with MS and the family caregivers: (1) information about available resources to support physical activity participation, with Need Indexes of 76.6% and 52.3%, respectively; (2) programs that support joint participation of people with MS together with their caregivers in physical activity, with Need Indexes of 62.0% and 68.9%, respectively; and (3) programs that have affordable total cost of participation, with Need Indexes of 50.7% and 52.3%, respectively. A broad range of factors (i.e., education, living situation, type of community, marital status, employment, and income, as well as comorbidity status) was significantly associated with one or more of these need items. Several modifiable impairment-related, personal and logistical factors were identified by both groups as barriers to co-participation in physical activity. Conclusions: The findings highlight the complexity of developing community resources that target physical activity promotion in MS dyads. Importantly, our findings suggest that resources designed to influence dyadic physical activity participation need to include content that are responsive and tailored to both the needs of the person with MS and the unique needs of the family caregiver. The results also underscore the importance of reinforcing physical activity as a shared behavior and providing information about affordable options for exercising together to the benefit of each individual and the dyad (i.e., partnership). Overall, our findings provide a possible starting point to guide the identification of potential participants that might benefit the most from future intervention development work. MS has life-altering consequences for people with the disease and the family caregivers who support such individuals. Rehabilitation professionals need to reinforce physical activity as a shared behavior and provide information about affordable options for exercising together to the benefit of each individual and the dyad. A "one-size-fits-all" approach is not appropriate, therefore, clinicians need to identify flexible and pragmatic strategies to increase dyadic participation in the presence of unique caregiver and care-recipients barriers that might impede such an increase.