Lepidoptera galls are induced by micromoths of distinct unrelated families. Galling Lepidoptera appear to have evolved from mining or boring insects, and their larvae exhibit chewing and voracious feeding behavior on the host plant tissues. Primarily considered as simple galls, several works have demonstrated distinct levels of complexity in lepidopteran galls. They may induce galls mainly on buds, stems, and leaves, harboring a single larva. Regardless of the host organ, lepidopteran galls are usually large and very conspicuous, sometimes with distinct colors and indumenta. Simple galls of Lepidoptera consist of hyperplasic tissues, with differentiation of nutritive cells. However, the most complex galls also involve parenchyma cell hypertrophy, rearrangement of vascular tissues or neoformation of vascular bundles, redifferentiation of sclerenchyma, lateral growth activity during gall maturity, and neoformation of altered leaf projections or emergences. The nutritive tissues usually accumulate lipids and proteins, while terpenes and starch may also be detected. Terpenoids and phenolic derivatives accumulate usually on the outer tissues of these galls, which may provide antioxidant protection of gall tissues and the larvae. Interactions with parasitoids may change the histochemical and anatomical profiles of these galls. Physiological effects of galling Lepidoptera, including alterations in photosynthesis rates and hormone accumulation are registered, yet further research is needed to understand the underlying molecular mechanisms and establish clear trends. Despite potential impacts on plant yield, their role as biological control agents for weeds seems limited and contingent upon environmental conditions, highlighting the need for additional studies to elucidate their ecological dynamics.