Because existing scales measuring internalized homonegativity suffer from various content validity flaws, a more valid instrument is needed. The purpose of this study was to develop and provide preliminary reliability and validity evidence for the Internalized Homonegativity Inventory (IHNI), which measures internalized homonegativity in gay men. Forty-two items were initially generated from a construct definition and were administered to 241 gay men living in the U.S. Exploratory factor analyses suggested that 23 items loaded on 3 subscales, which were labeled Personal Homonegativity, Gay Affirmation, and Morality of Homosexuality. IHNI scores correlated in expected directions and magnitude with measures of extroversion, emotional stability, stage of gay identity development, and another internalized homonegativity instrument. Implications of the three-factor structure of the IHNI for the conceptualization of internalized homonegativity are discussed.