We evaluated the effect of dimethyl fumarate (DMF) treatment on B-cell memory and cytokine production in 18 patients with relapsing remitting multiple sclerosis (RRMS) using peripheral blood mononuclear cells obtained prior to and at 6 months post-DMF initiation. We noted a decline in the absolute B-cell number with DMF treatment, with a preferential depletion of memory B cells and a concurrent increase in naïve B cells. We noted significant reductions in GM-CSF, TNF-α, and IL-6 producing B cells with DMF treatment. These effects on the B-cell compartment may underlie the beneficial effects of DMF in RRMS.