Background: Obesity induces neuroinflammatory effects on the central nervous system (CNS) through dysregulation of energy metabolism, inflammation, and immune responses. Obesity is associated with poor clinical response of multiple sclerosis (MS) to immune mediator drugs. We aimed to assess IL-17 serum and mRNA levels in MS patients and to explore the association of obesity with DMT response and IL-17 serum and mRNA levels in patients with MS. Methods: we examined 40 patients with MS, the diagnosis was according to the latest 2017 McDoland criteria, and 40 subjects as a control group. IL-17 mRNA and serum levels of IL-17 were determined by ELISA. Results: 40 patients with MS were included, of whom 15 (37.5%) were obese, and 25(62.5%) patients were lean. IL-17 mRNA level was significantly higher in the obese MS group (3.4±1.24) compared to the lean MS group (2.5±1.11) and control group (0.9±0.09), P <0 .001. Also, IL-17 level was significantly high in the obese group (46.75±12.2) compared to the lean group (36.23±9.2) and the control group (23.1±5.7), P <0 .001. MS patients treated with fingolimod had statistically significant lower levels of IL-17 mRNA and serum IL-17 compared to patients treated with Interferon beta-1a and b. These markers were associated with BMI, number of relapses in the last 2 years, Expanded Disability Status Scale (EDSS), ESR, and hs-CRP. Conclusions: IL-17 serum and mRNA levels were upregulated in MS patients, particularly obese patients. MS patients treated with fingolimod had statistically significant lower levels of IL-17 mRNA and serum IL-17 compared to other patients.