Backround The fumaric acid ester (FAE) dimethylfumarate (DMF) is a small molecule immunomodulator successfully used for the treatment of psoriasis and multiple sclerosis (MS). DMF is thought to inhibit pathogenic immune responses with Th17/Th1 T cells, and IL-23/IL-12 producing dendritic cells (DCs). 6-sulfo LacNAc expressing dendritic cells (slanDCs) are a human pro-inflammatory cell type found frequently among the infiltrating leukocytes in skin lesions of psoriasis and brain lesions of MS. Objective To explore the influence of DMF on functional properties and cell signaling pathways of slanDCs. Methods In the context of slanDCs we studied the role of DMF in modulating cell migration, phenotypic maturation, cytokine production, cell signaling and T cell stimulation. Results Initially, we observed the reduction of slanDCs numbers in psoriasis skin lesions of FAE treated patients. Studying whether DMF controls the migratory capacity of slanDCs to chemotactic factors expressed in psoriasis we observed an inhibition of the CX3CL1 and C5a depedent cell migration. DMF also attenuated the rapid spontaneous phenotypic maturation of slanDCs, as judged by a reduced CD80, CD86, CD83 and HLA-DR expression. In addition, we observed a DMF-dependent decrease of IL-23, IL-12, TNF-α and IL-10 secretion, and noticed a reduced capacity to stimulate Th17/Th1 responses. DMF targeted in slanDCs different intracellular cell signaling pathways including NFκB, STAT1 and HO-1. Conclusions With this study we identify a frequent pro-inflammatory cell type found in psoriasis and MS as a relevant target for the therapeutic immunomodulatory effects of DMF.