MHC-restricted T cells require the CD8 and CD4 co-receptors to interact with MHC class I and class II molecules respectively, supporting the notion that T cells lacking these co-receptors likely interact with antigen-presenting molecules other than MHC, such as CD1 and MR1. Known unconventional T cells within the CD4-/CD8- double negative (DN) αβ T cell fraction include iNKT cells and MAIT cells, as well as reports of DN T cell clones restricted by CD1a, CD1b, or CD1c molecules. This broad CD1-dependence within the DN T cell population, beyond iNKT cells, remains incompletely explored. Clinically, the DN αβ T cell population is relevant, given that this population is known to expand in autoimmune conditions such as systemic lupus erythematosus (SLE). Using CD1a, CD1b, CD1c, and CD1d tetramers that were not treated with exogenous lipid and therefore contained an endogenous lipid repertoire (CD1-endo), we determined the ex vivo frequencies of CD1 tetramer+ T cells within the DN T cell repertoire. In a panel of 11 ex vivo healthy donor peripheral blood mononuclear cells (PBMCs), CD1-endo tetramer+ T cells were overrepresented in the TCRαβ+/DN fraction for all CD1 isoforms. We observed an average 9-fold and 15-fold increase in CD1 tetramer+ T cells in the DN subset as compared to CD4+ and CD8+ T cells, respectively. In vitro, expansion of DN T cells resulted in CD1-endo staining T cell lines, confirming the ex vivo data. These CD1-endo tetramer+ T cells were CD1-autoreactive, as determined by CD1-dependent TCR downregulation in response to CD1-transfected antigen-presenting cell lines. Overall, we have confirmed the notion that the human DN-T cell repertoire is enriched for CD1-autoreactive T cells.