Metabolic syndrome constitutes a cluster of metabolic abnormalities including central obesity, hypertension, insulin resistance and atherogenic dyslipidemia, which are associated with an increased risk of cardiovascular disease. A growing body of evidence suggests that obesity, and components of the metabolic syndrome (MetS) influence the risk of multiple sclerosis (MS) or outcomes after MS onset. Specifically, obesity is associated with an increased risk of developing MS. Obesity and the components of MetS are associated with longer diagnostic delays from symptom onset to diagnosis, relapse rates, disability progression, brain atrophy and mortality. Obesity may also influence the effectiveness of disease-modifying therapy. These findings have important implications for disease management.