Inclusion of wildlife in the concept of One Health is important for two primary reasons: (1) the physical health of humans, domesticated animals, and wildlife is linked inextricably through shared diseases, and (2) humans' emotional well-being can be affected by their perceptions of animal health. Although an explicit premise of the One Health Initiative is that healthy wildlife contribute to human health, and vice versa, the initiative also suggests implicitly that wildlife may pose threats to human health through zoonotic disease transmission. As people learn more about One Health, an important question surfaces: How will they react to communications carrying the message that human health and wildlife health are linked? In the absence of adequate relevant research data, we recommend caution in the production and dissemination of One Health messages because of possible unintended or collateral effects. Understanding how and why individuals perceive risks related to wildlife diseases is essential for determining message content that promotes public support for healthy wildlife populations, on the one hand, and, on the other, for identifying messages that might inadvertently increase concern about human health effects of diseased wildlife. To that end, we review risk perception research and summarize the few empirical studies that exist on perceived risk associated with zoonoses. We conclude with some research questions that need answering to help One Health practitioners better understand how the public will interpret their messages and thus how to communicate positively and without negative collateral consequences for wildlife conservation.