There are still many gall systems associated with larvae of Lepidoptera in which the true gall-inducers have not been identified to species. Reports on misidentification of gall inducers have been recurrent for these galls, particularly in complex gall-systems that may include inquilines, kleptoparasites, and cecidophages, among other feeding guilds such as predators and parasitoid wasps. Here we describe and illustrate the adults, larvae, pupae and galls, based on light and scanning microscopy, of Andescecidiumparrai gen. et sp. n.and Olierasaizi sp. n., two sympatric cecidosid moths that are associated with Schinuspolygamus(Cav.) Cabrera (Anacardiaceae) in central Chile. Adults, immatures, and galls of the former did not conform to any known cecidosid genus. Galls of A.parraiare external, spherical, and conspicuous, being known for more than one century. However, their induction has been mistakenly associated with either unidentified Coleoptera (original description) or OlieraargentinanaBrèthes (recently), a distinct cecidosid species with distribution restricted to the eastern Andes. Galls of O.saizihad been undetected, as they are inconspicuous. They occur under the bark within swollen stems, and may occur on the same plant, adjacent to those of A.parrai. We also propose a time-calibrated phylogeny using sequences from mitochondrial and nuclear loci, including specimens of the new proposed taxa. Thus in addition to clarifying the taxonomy of the Chilean cecidosid species we also tested their monophyly in comparison to congeneric species and putative specimens of all genera of Neotropical and African cecidosids.