Four independent studies conducted in three different countries evaluated the strength of the Genderism and Transphobia Scale (GTS; Hill & Willoughby, 2005), a recently developed measure of anti-trans sentiments and behaviors. Study 1 utilized the GTS to examine anti-trans attitudes among mental health professionals. Study 2 employed the GTS to evaluate the effects of personal contact with transpersons, conformity, and perceived threat to social cohesion on attitudes toward gender nonconformity. Study 3 examined the reliability, validity, and factor structure of the GTS among college students in the Philippines. Lastly, Study 4, conducted in Canada, used variables from the general literature on prejudice to create a comprehensive model predicting genderism and transphobia. Collectively, results of this multinational, multisite study further support the reliability and validity of the GTS and elucidate factors associated with anti-trans sentiments and behaviors.