Multiple sclerosis (MS) is a multicomponent disease that is marked by continual inflammation, demyelination and irreparable damage to the central nervous system. While it was long thought to be mediated by T cells, B cells are now understood to be a central component of MS pathology. Dysfunction and aberrant activity of antigen presenting cells, T cells and B cells are all part of the pathophysiology of the disease. B cells and plasma cells contribute to disease progression through multiple mechanisms, including cytokine secretion, antibody production and antigen presentation. More recent evidence suggests that B cells may play a larger role than previously thought in driving acute episodes of MS. In this review we explore the classical understanding of MS, the evidence and current understanding of B cells in the central nervous system in health and disease, and the interactions present between B cells in the central nervous system and the peripheral nervous system. Lastly, we explore targeted immunological treatments which affect B cells and how this has informed our understanding of MS.