Multiple Sclerosis (MS) and Rheumatoid Arthritis (RA) are amongst the most common autoimmune diseases in the northern hemisphere. There is mounting evidence that in both afflictions, not only environmental and genetic factors influence disease, but cellular components such as autoreactive T cells also contribute to pathology. Animal models are key in the study and subsequent therapeutic development for human autoimmune diseases. As patient material is often difficult to obtain and in some cases--as in MS, where the central nervous system (CNS) is concerned--even not accessible, animal models provide a multifaceted tool to explore disease-underlying mechanisms. The pro-inflammatory T cell cytokine IL-17 has recently moved to center stage due to its crucial role in autoimmune diseases including MS and RA. A plethora of studies in animal models has sustained the relevance of this cytokine pathway for the development of autoimmunity and shed light on its cellular sources and patho-mechanisms. This review addresses the role of IL-17 producing T lymphocytes, in particular CD4(+) and γδ T cells, in three commonly used mouse models for MS and RA, namely experimental autoimmune encephalomyelitis (EAE), collagen-induced arthritis (CIA), and antigen-induced arthritis (AIA). Comparing and combining knowledge gained from different animal models will broaden our understanding of the IL-17 biology and facilitate the translation to the human diseases.