Virtual influencers on social media are an intriguing phenomenon on the rise. They are computer-generated characters that attract a large number of followers and audiences who interact and engage with virtual influencers. Audience engagement with virtual influencers is an interesting phenomenon; yet little is known about the motivation and essence of such engagement. This research takes a qualitative approach of netnography to study audience engagement with virtual influencers. Content analysis on audience comments left on three virtual influencers' Instagram accounts (including Miquela, Noonoouri, and Guggimon) is conducted. Four major content themes emerge in audience comments: emotional attachment, source admiration, novelty, and expertise. We propose a conceptual model that postulates the impacts of these factors on engagement, moderated by the anthropomorphism of virtual influencers. This research reveals insights into drivers of audience engagement with virtual influencers, providing a theoretical model and practical implications.