Glucosinolates (GS) are the important secondary metabolites of Brassicaceae plants, playing an important role in regulating the interrelationships between Brassicaceae plants and insects. GS can protect Brassicaceae plants against euryphagous herbivorous pests because of the toxicity of GS and their breakdown products. However, oligophagous pests which have evolved manifold metabolic pathways to cope with the defensive compounds depended fully on GS and their volatile breakdown products for host-plant recognition and orientation. The GS ingested by herbivores are also toxic to carnivores, and can directly deter predators. On the other hand, predators and parasitoids are attracted by the volatile breakdown products of GS from the Brassicaceae plants damaged by herbivores. Based on the recent findings, this paper reviewed the defensive function of GS against herbivores, host selection of oligophagous pests, GS metabolic pathways of herbivores, induction of GS by herbivores, and effects of GS on the third tropic level. Future directions and techniques in this research field were also suggested.