Exotic spiders are common in a wide range of ecosystems, yet little is known about their ecological impacts. Yellow sac spiders of the genus Cheiracanthium (Miturgidae) have been particularly successful in invading a variety of ecosystems. One species, C. mildei, often dominates the spider fauna in crop systems such as vineyards. We conducted surveys to provide a foundation for assessing the impact of C. mildei on herbivores and native arthropod predators. C. mildei was most abundant in vineyards with an impoverished native spider fauna, suggesting it may impact the native spider community, either by competition or intraguild predation. Landscape context also appeared to influence spider composition in vineyards, with vineyards surrounded by oak woodland having higher spider species diversity and lower proportions of C. mildei than vineyards far from any natural vegetation.