Alliaria petiolata is a European biennial herb that invades North American forests and has direct negative effects on associated flora and fauna. In some places, A. petiolata has invaded the habitat of Pieris virginiensis, a rare, univoltine butterfly that normally uses native spring ephemeral crucifer hosts. There are occasional observations of P. virginiensis laying eggs on A. petiolata, but the frequency and effects of these “mistake oviposition events” are not yet known. We investigated P. virginiensis oviposition preference through field observations in three locations (NY, OH, PA), and also through laboratory experiments measuring egg deposition of adult females on either a native or invasive crucifer. In addition, we examined neonate larval performance through no-choice feeding assays on both A. petiolata leaves and cabbage leaves painted with A. petiolata leaf extracts. We found that P. virginiensis lays significantly more eggs on the exotic A. petiolata than on its native host Cardamine diphylla in both field and laboratory experiments. Caterpillars fed either A. petiolata leaf tissue or its ethanol extract did not survive to pupation, and most died after only a few days. Continual invasion and persistence of A. petiolata in P. virginiensis habitats may lead to genetic bottlenecking and possibly local extinctions without human intervention