Antisocial attitudes have been identified as a powerful predictor of criminal behavior, but currently-existing measures for these all rely on individuals to accurately self-report their attitudes, which they often have incentives not to do. The Implicit Test of Antisocial Attitudes (ITAA) is an adaptation of the Implicit Associations Test (IAT) which attempts to address this shortcoming by measuring antisocial attitudes without relying on examinee self-report. The current study describes the construction and derivation of the ITAA, and examines the reliability and validity of the ITAA using responses from a justice-involved sample of incarcerated men and a non-justice-involved sample of men and women in the community. Results are broadly favorable for the psychometric characteristics of the ITAA. Implications and directions for future studies are discussed.