The introduction of non-native organisms is a leading cause of species imperilment, especially on oceanic islands. This study examines the impact of an invasive yellowjacket, Vespula pensylvanica. Because Hawaii has no native social insects, endemic arthropods may be particularly sensitive to predation and competition from this invasive wasp. We investigated the predatory effects of V. pensylvanica invasions on native arthropods, which compose more than 25% of the yellowjacket diet. Experimental removal of V. pensylvanica colonies resulted in significant increase in the local abundances of larval Lepidoptera and Araneae. Examination of the competitive interactions between endemic solitary Hymenoptera and yellowjackets revealed that endemic bees and wasps do not forage in the vicinity of yellowjacket nests. Trap nest data also indicate that the presence of yellowjacket nests in the fall influences the distribution and abundance of solitary wasps in the subsequent spring. These trends persisted for months following colony removal, indicating that V. pensylvanica exert considerable predatory and competitive pressure on local arthropod populations.