Inactivity is a prevalent problem in the population affected with multiple sclerosis (MS). Thus, there is a need to develop and test physical activity (PA) interventions that can be widely disseminated. We conducted a formative evaluation as part of a randomized controlled trial of a pamphlet-based PA intervention among 30 women with MS. Pamphlets were customized to sub-sets of participants who shared similar symptoms and barriers to PA. Mixed methods were used to examine the intervention's influence on self-efficacy, social support, processes of change and stages of change placement, as well as explore participants' perceived barriers, motivators and strategies for engaging in a PA program. Results indicated that the intervention group significantly improved stages of change placement (F = 16.64, P < 0.01) and social support (F = 4.08, P = 0.05) in comparison to the control group. Fatigue, pain and lack of time were the commonly cited barriers to engage in the PA program; whereas the pamphlets, phone calls and action planning were cited as motivators. Participants used fatigue management strategies, enlisted social support and modified their environment to routinely engage in the PA program. Strategies were identified to improve the PA intervention in future research.