Purpose: People with multiple sclerosis (PwMS) and their family caregivers often react to the impact of the disease as an interdependent dyad. The aim of this exploratory study was to examine interdependence in the physical activity (PA) patterns of dyads affected by moderate to severe MS disability. Method: A total of 15 pairs of PwMS and their family caregivers wore accelerometers for 7 days. By collecting data simultaneously from both partners, we tested interdependence using the dyad as the unit of analysis. Results: PwMS and caregivers averaged 4,091.3 (SD 2,726.3) and 6,160.2 (SD 1,653.0) steps per day, respectively. The mean number of minutes per day of sedentary, light, and moderate to vigorous activity for PwMS was 566.3 (SD 97.7), 167.4 (SD 94.0), and 7.6 (SD 12.4), respectively, and 551.9 (SD 92.4), 199.6 (SD 63.4), and 21.4 (SD 18.2), respectively, for caregivers. Interdependence between dyads for sedentary, light, moderate to vigorous activity, and step count was low and non-significant (rs=0.20, 0.26, 0.13, and –0.27, respectively; p>0.05). Conclusions: Although our findings do not support the interdependence of PA between caregivers and care recipients with MS, they do show that both partners are not engaging in sufficient PA to achieve important health benefits. These findings are important because they indicate that the dyads are likely to benefit from interventions for changing PA behavior.