The study aimed to develop the Homophobic Bullying Scale and to investigate its psychometric properties. The items of the Homophobic Bullying Scale were created to measure high school students' bullying behaviors motivated by homophobia, including verbal bullying, relational bullying, physical bullying, property bullying, sexual harassment, and cyberbullying. Five scales were developed from viewpoints of bullies (toward supposed gay men and lesbians), victims, and witnesses (toward supposed gay men and lesbians). A sample of 863 students enrolled in Grades 9 to 13 in 10 Italian public high schools were involved in this study. The coefficients of internal consistency were greater than .80 for all the scales. Construct validity of its factor structure was demonstrated using confirmatory factor analysis. Discriminant validity was demonstrated by comparatively low correlations with homophobic attitudes and the Homophobic Content Agent Target scale. Results showed the existence of homophobic bullying in various forms other than the use of homophobic epithets. Future research should examine the experience of bullying behaviors motivated by homophobia in schools. (Contains 3 tables.)