The current study presents the initial validation of a new 20-item measure of heterophobia, a construct frequently discussed but inadequately researched in the literature on gay men’s lives. This process included initial focus groups, exploratory and confirmatory national samples of gay men. The sample included measures of homophobia, rejection sensitivity, discrimination history, gay identity development, and social desirability to address convergent and discriminant validity. Results of an exploratory factor analysis yielded three meaningful factors: Disconnectedness, Expected Rejection, and Unease/Avoidance. These factors had significant positive associations with constructs such as rejection sensitivity, homonegativity, and previous experiences of gay-related discrimination, but were only weakly associated with gay identity development. Heterophobia factors had insignificant or negative correlations with social desirability. This factor structure was supported by the results of confirmatory factor analyses. Implications for future research and clinical practice, along with limitations, are provided.