People with multiple sclerosis (MS) fall frequently. Poor walking aid selection, fit, and use contribute to falls in those who use walking aids. To determine if the Assistive Device Selection, Training, and Education Program (ADSTEP), with six weekly one-on-one virtual sessions with a physical therapist prevents falls and improves other outcomes in people with MS who use walking aids but still fall. A total of 78 people were randomized to ADSTEP or control. Participants recorded falls daily through 6 months post-intervention. Other outcomes were assessed at baseline, intervention completion, and 6 months later. Outcomes were compared between groups. The ADSTEP group's mean fall rate (falls/person/month) decreased from baseline to intervention completion (ADSTEP = -0.75, control = +0.90, p < 0.001) and to 6 months later (ADSTEP = -1.02, control = +0.03, p = 0.017) compared to controls. At 6 months, the ADSTEP group had improved physical activity (days/week walking ⩾ 10 minutes at a time: ADSTEP = +0.69, control = -0.58, p = 0.007; minutes/day sitting: ADSTEP = -57, control = +56, p = 0.009) and walking aid fit (proportion with good fit: ADSTEP = +25%, control = -13%, p = 0.018) compared to controls. ADSTEP likely reduces falls, increases physical activity, and improves walking aid fit in people with MS who use walking aids and fell in the past year.