The purpose of this study was to develop and validate 2 gender identity implicit association tests (GI-IATs) designed to assess attitudes toward transsexual men (Transmen-IAT) and transsexual women (Transwomen-IAT). A sample of 344 Mechanical Turk participants from the United States (173 women, 129 men, 43 transgender) completed the following: GI-IATs, Genderism and Transphobia Scale, Allophilia Toward Transsexual Individuals Scale, Social Desirability Scale-17, feelings thermometers, and ratings of intention to support transgender workplace policies. Results indicate that people who are cisgender (non-transgender), heterosexual, politically conservative, or who reported no personal contact with transgender individuals showed cisgender preferences on both GI-IATs. Additionally, both measures correlated as predicted with the explicit measures (feeling thermometers) of attitude toward transgender individuals. As expected, the explicit attitude measures, but not the GI-IATs, correlated with social desirability. Further, confirmatory factor analyses supported the model comprising 4 distinct latent variables: implicit attitudes toward transmen, explicit attitudes toward transmen, implicit attitudes toward transwomen, and explicit attitudes toward transwomen. Finally, hierarchical multiple regressions showed that both explicit and implicit measures predicted support for transgender workplace policies. Additional analyses showed that both the Transmen-IAT and the Transwomen-IAT accounted for incremental variance above and beyond the relative feelings thermometers in predicting policy support intentions. These findings provide significant psychometric support for both GI-IATs. They also highlight the importance of incorporating implicit measures in studying attitudes toward transgender individuals, and of distinguishing attitudes toward transmen versus transwomen.