Invariant natural killer T (iNKT) cells are thymus-generated innate-like αβ T cells that undergo terminal differentiation in the thymus. Such a developmental pathway differs from that of conventional αβ T cells, which are generated in the thymus but complete their functional maturation in peripheral tissues. Multiple subsets ofiNKT cells have been described, among which IL-17-producingiNKT cells are commonly referred to as NKT17 cells. IL-17 is considered a proinflammatory cytokine that can play both protective and pathogenic roles and has been implicated as a key regulatory factor in many disease settings. Akin to otheriNKT subsets, NKT17 cells acquire their effector function during thymic development. However, the cellular mechanisms that drive NKT17 subset specification, and howiNKT cells in general acquire their effector function prior to antigen encounter, remain largely unknown. Considering that alliNKT cells express the canonical Vα14-Jα18 TCRα chain and alliNKT subsets display the same ligand specificity, i.e., glycolipid antigens in the context of the nonclassical MHC-I molecule CD1d, the conundrum is explaining how thymic NKT17 cell specification is determined. Mapping of the molecular circuitry of NKT17 cell differentiation, combined with the discovery of markers that identify NKT17 cells, has provided new insights into the developmental pathway of NKT17 cells. The current review aims to highlight recent advances in our understanding of thymic NKT17 cell development and to place these findings in the larger context ofiNKT subset specification and differentiation.