Objective. To examine knowledge of Zika transmission and risk perception and to assess variability by condom use in a probability sample of sexually-active adults in the United States. Methods. Data for this study came from the 2016 wave of the National Survey of Sexual Health and Behavior, a nationally representative probability sample of adults in the United States. Data were collected in November 2016 via a cross-sectional Internet-based survey administered to members of a Knowledge Panel, an address-based random sample service managed by GfK. A weighted subsample (n = 1 713) of sexually active adults, 18 – 50 years of age, was included in analyses. Results. More than 90% of men and women reported low or no perceived risk of Zika. Most participants identified mosquito bite as a route of transmission, while significantly fewer identified sexual intercourse (≈ 40%) and vertical (29% men, 41% women) transmission routes. Conclusion. Sexually-active adults in the United States, especially young men, lack awareness of sexual and vertical transmission of Zika Virus. Given the likely endemic nature of Zika, this low-risk perception is an important prevention challenge. Zika prevention messaging should address lesser known transmission routes, emphasize male education, and promote correct and consistent condom use.