Fear is a pervasive aspect of political life and is often explored as a transient emotional state manipulated by events or exploited by elites for political purposes. The psychological and psychiatric literatures, however, have also established fear as a genetically informed trait, and people differ in their underlying fear dispositions. Here we propose these differences hold important implications for political preferences, particularly toward out-groups. Using a large sample of related individuals, we find that individuals with a higher degree of social fear have more negative out-group opinions, which, in this study, manifest as anti-immigration and prosegregation attitudes. We decompose the covariation between social fear and attitudes and find the principal pathway by which the two are related is through a shared genetic foundation. Our findings present a novel mechanism explicating how fear manifests as out-group attitudes and accounts for some portion of the genetic influences on political attitudes.