The predatory bug Anthocoris nemoralis (F.) is a common species native to Europe that has become established in several areas of North America. The objectives of this study were to determine whether North American and European insects differed in aspects of mating activity and reproduction. We compared mating preferences, mating propensities, and some life history traits between a European (England) and North American (San Francisco Bay area) population of A. nemoralis; the North American population colonized the source locale apparently between 10 and 30 yr ago. In no-choice and choice assays, the insects showed no preference for mating with insects from the same source population. Both types of assays indicated that insects from the two sources differed in mating propensities: UK females were less likely to mate during a 30-min assay than females from California (irrespective of male source); and California males were less likely to mate than males from the UK (regardless of female source). More than 80% of mated females matured ovaries from all population crosses. Copulation duration was shorter in pairings involving California males (13.8 min) than matings involving UK males (16.9 min). The preoviposition period averaged ≈3 d for females from both populations. Insects of both sexes from both populations were able to mate within 24–48 h of adult eclosion. Younger males of both populations copulated longer and were less likely to prompt ovarian maturation in the female than older males. Several characteristics of A. nemoralis, including its generalist feeding habits, rapid maturation, short preoviposition period, and low levels of mating discrimination may help explain why this species has been successful in colonizing new geographic areas.