Juvenile hormone (JH) plays a crucial role in regulating insect diapause, a physiological state of developmental or reproductive arrest that allows insects to synchronize their life cycles with favorable environmental conditions. This chapter provides an overview of the current knowledge on the role of JH in insect diapause at various developmental stages. In adult diapause, a low JH titer in the hemolymph is the main cause of diapause induction and maintenance. JH controls adult diapause through canonical signaling pathways involving Methoprene-tolerant, Taiman, and Krüppel homolog 1 as well as noncanonical pathways that may be species-specific. In contrast, the roles of JH in embryonic, larval, and pupal diapause are more variable. Although JH may induce embryonic diapause in some species, it plays little or no role in other species. In larval and pupal diapauses, a shutdown of the brain–prothoracic gland axis and the resulting lack of ecdysteroids is a general feature; however, JH can also induce diapause in some species by maintaining high titers. This chapter further discusses the role of JH in the maternal effects on diapause induction in the next generation.