Background: Multiple sclerosis (MS) is the most common permanent neurological disorder affecting young adult causing strength deficits. Aim of the study: This study was conducted to investigate influence of selected aerobic exercises on serum Vitamin D level and lower limb performance in patients with multiple sclerosis. Subjects and methods: 30 patients with relapsing remitting MS recently diagnosed with early stage of MS, vitamin D insufficiency less than 20-30 ng/mL, age from 20 to 40 years old and body mass index less than 25 kg/m² were recruited, assessed for and assigned into 2 groups. They received treatment program as follows: control group (A) received conventional medical treatment (Corticosteroids, Interferon beta medications, Dimethyl fumarate, muscle relaxants, medications to reduce fatigue) in addition to vitamin D supplementation only, while experimental group (B) received conventional medical treatment, vitamin D supplementation in addition to selected aerobic exercises. The outcome measures included serum vitamin D level by lab test, timed 25 walk test by measure timing of performance of lower limb gait in multiple sclerosis. Results: both groups showed significant difference in the outcome measures in the post treatment assessment, but the selected aerobic exercises (B) showed a more significant improvement over the control group at p-value >0. 001. Conclusion: selected aerobic exercises is an effective physical therapy modality when added to the conventional medical treatment, so it may provide better outcomes for serum vitamin D level and lower limb performance in patients with MS.