Sport sponsorship is an important marketing communication tool, and stakes in sponsorship deals are high. Therefore, sponsors strive to ensure that their investments are effective and protected from competitors—that is, ambusher marketers’ attacks. Still, little is known about how ambush marketing affects sponsor identification and misidentification of ambushers as sponsors. This study investigates levels of sponsor and ambusher identification in three experimental settings, controlling for the presence/absence of an ambusher, communication modality, and response formats. A field study in the context of a large sports event demonstrates the external validity of the findings. The results provide evidence of a nondestructive interference of ambush marketing, indicating that ambush marketing does not necessarily harm sponsor identification. Misidentification of nonsponsors as sponsors occurs because of the indirect link established between the event and the company through ambush marketing, but not as a consequence of other communication activities by a competitor with no link to the event. Finally, a combined sponsor–ambusher perspective indicates that sponsors do not necessarily have a consistent “official sponsor” advantage over ambushers. Findings are discussed with emphasis on implications for sponsors, ambushers, and marketing researchers.