<jats:title>Abstract</jats:title> <jats:p>Protein Arginine Methyltransferase (PRMT) 5 is a type-II methyltransferase involved in oncogenesis, embryonic and hematopoietic development. However, the role of PRMT5 T-cell biology is only now coming into focus. To evaluate PRMT5’s functions in T-cells, we have developed a conditional knock-out (KO) model that allow for a deletion of PRMT5 during thymic development, by knocking-out PRMT5 in all peripheral T cells (T-PRMT5D/D). Using this model that deletes both protein-coding isoforms of Prmt5, we investigated the role of the PRMT5 gene during T-cell development, proliferation and experimental autoimmune encephalomyelitis (EAE). We saw reduced numbers of CD4+ T-cells, Tregs and iNK T-cells in the thymus. CD4+, Treg and iNK T-cell number defects were seen in the peripheral lymphoid organs such as spleen and lymph nodes. Peripheral analyses also showed reduced CD8+ T-cells, naive, effector and central memory CD4+ T-cells. We also induced PRMT5 deletion specifically in peripheral CD4+ T cells (iCD4-PRMT5D/D). We utilize this model to induce PRMT5 deletion specifically in peripheral CD4+ T cells while ensuring that the mice develop normal numbers of peripheral T cells. Using this model, we showed that EAE was completely abolished in the mice. Total CNS infiltrating T-cell numbers were substantially reduced, and significant losses were observed in the Th1 and Th17 cytokine production from these cells. These data substantively demonstrate a driver role for PRMT5 in thymic CD4 Th cell development, peripheral CD4+, iNKT and CD8+ T-cell maintenance and Th cell-mediated EAE autoimmunity.</jats:p>