An increasing number of children in the U.S. and around the world are exposed to multiple languages, yet there is considerable variation in individual bilingual outcomes. Previous research has shown that factors such as input, usage, and language history can help explain this variation, but less is known about the role of attitudes towards bilingualism, and no instrument currently exists for measuring such attitudes. Guided by previous theories on language perceptions, we describe two new scales developed to measure general perceptions of the value of bilingualism (study 1: Perceptions of Bilingualism, PoB) and parental perceptions of the value of bilingualism for one’s child (study 2: Perceptions of Bilingualism for child, PoB+) in the United States. We use factor analysis and Item Response Theory (IRT) to test the reliability, dimensionality, and individual item contributions of each scale using a national online sample of 422 adults (study 1) and a subsample of 321 parents (study 2). The final 10 and 8-item scales demonstrate internal reliability, unidimensionality, and precision of the intended construct to be measured. We report associations between scale scores and demographic characteristics and discuss how an IRT approach can complement classical approaches to attitude scale development. The PoB and PoB+ are useful tools to explore the association between social perceptions of bilingualism and language use for oneself and for one’s child.