The purpose of this research was to develop and validate a conceptually and psychometrically solid measure for patriarchal beliefs in samples of U.S. American adults from diverse demographic and geographic backgrounds. In Study 1, we identified 3 correlated factors of the Patriarchal Beliefs Scale (PBS) in data collected from the Internet (N = 279): Institutional Power of Men, Inferiority of Women, and Gendered Domestic Roles. In Study 2, data collected from the Internet (N = 284) supported both an oblique 3-factor structure and a bifactor structure of the PBS, through confirmatory factor analyses. Construct validity of the PBS was supported in relation to other gender-related measures. The PBS was correlated in expected directions with modern sexism, antifeminist attitudes, and egalitarian attitudes toward women. In Study 3, we examined measurement invariance across gender by using combined data from Study 1 and Study 2. All 3 factors of the oblique 3-factor model indicated measurement invariance, whereas the general factor represented in the bifactor model indicated nonequivalence. Mean differences in patriarchal beliefs were found for such demographic variables as gender, sexual orientation, education, and social class. Recommendations for using the PBS, as well as implications for research and practice, are discussed.