Hymenopteran and dipteran parasitoids of slug moth caterpillars (Lepidoptera: Limacodidae) from North America are reviewed, and an illustrated key to 23 genera is presented. Limacodid surveys and rearing were conducted during the summer months of 2004–2009 as part of research on the ecology and natural history of Limacodidae in the mid-Atlantic region of the U.S.A. Parasitoid rearing involved a combination of collecting naturally occurring larvae in the field (at least 14 host species) and placing out large numbers of “sentinel” larvae derived from laboratory colonies of three host species. Species in the following families are documented from limacodids in North America as primary or secondary parasitoids (number of genera for each family in parentheses; number of genera included in key but not reared through this research in brackets): Chalcididae ([1]; Hymenoptera: Chalcidoidea), Eulophidae (3; Chalcidoidea), Pteromalidae ([1]; Chalcidoidea), Trichogrammatidae (1; Chalcidoidea), Braconidae (3 [1]; Hymenoptera: Ichneumonoidea), Ichneumonidae (7 [3]; Ichneumonoidea), Ceraphronidae (1; Hymenoptera: Ceraphronoidea), Trigonalidae (2; Hymenoptera: Trigonaloidea), Bombyliidae ([1]; Diptera: Asilioidea), and Tachinidae (3; Oestroidea). We recovered 20 of 28 genera known to attack limacodids in North America. Records discerned through rearing in the mid-Atlantic region are augmented with previously published host-parasitoid relationships for Limacodidae in North America north of Mexico. New records are reported for the following parasitoids (total new records in parentheses): Uramya limacodis (Walker) (1), U. pristis (Townsend) (5), Austrophorocera spp. (6), Ceraphron sp. (1), Alveoplectrus lilli Gates (1), Playplectrus americana (Girault) (10), Pediobius crassicornis (Thomson) (1), Trichogramma (1), Mesochorus discitergus (Say) (1), Hyposoter fugitivus (Say) (1), and Isdromas lycaenae (Howard) (5). The male of Platyplectrus americana (Hymenoptera: Eulophidae) is redescribed, and the female is described for the first time. Incidental and miscellaneous host-parasitoid associations are discussed, and it is concluded that most of these records are likely parasitoids of contaminants accidentally introduced during the limacodid rearing process. Triraphis eupoeyiae (Ashmead), new combination, is transferred from Rogas (Hymenoptera: Braconidae).