Nuclear energy has long been assumed to elicit automatic, negative reactions. However, little research has investigated implicit associations with nuclear energy. To assess implicit and explicit attitudes toward nuclear energy, 704 U.S. consumer panelists completed a multicategory Implicit Association Test (IAT) and an Internet survey. Results showed that participants held negative implicit attitudes toward nuclear energy (vs. wind and natural gas) and positive implicit attitudes toward nuclear energy (vs. coal). Strong opponents of nuclear policy implicitly preferred natural gas over nuclear and implicitly disliked nuclear as much as coal. Strong supporters of nuclear policy implicitly preferred nuclear over coal, and showed no implicit preference for gas over nuclear. Implicit attitudes toward nuclear energy (vs. gas and wind) were related to policy support when controlling for explicit attitudes and demographics. Understanding both implicit and explicit nuclear attitudes is important for decision makers as the United States charts its energy future.