One approach to plagiarism prevention focuses on improving students' authorial identity, but work in this area depends on robust measures. This paper presents the development of a psychometrically robust measure of authorial identity--the Student Attitudes and Beliefs about Authorship Scale. In the item generation phase, a pool of items was developed and assessed for content validity by subject matter experts. In the exploratory phase, data from 439 higher education students were used to identify a latent variable model with three factors: "authorial confidence," "valuing writing" and "identification with author." In the confirmatory phase, data from 306 higher education students were used to test the three-factor model's reliability and validity. The three-factor structure was confirmed, and the results showed that the SABAS has a stronger psychometric basis than previously available measures. This measure of authorial identity can be used with confidence in research and pedagogy to help students improve their authorial identity.