Political interest is one of the strongest predictors of individual political engagement, but little is known about the origins of this political orientation. The goal of this paper is to clarify the role that biological and psychological factors play in the formation of political interest. A series of recent studies in genetics have illustrated that political interest is heritable, and a series of recent studies in political science and psychology have demonstrated that personality traits, many of which are heritable, are related to political interest. In this paper, we make a number of contributions to the literature: (1) we replicate previous analyses showing that political interest and personality traits are heritable, (2) we demonstrate that personality traits are related to interest, and (3) we estimate the extent to which genetic factors account for the correlation between personality traits and political interest. Using two datasets on twins, we find evidence that genetic factors account for a large amount of the correlation between political interest and personality traits. This study provides a more nuanced picture of the biological and psychological bases of political orientations.