Introduction: The legal advances in recognizing the rights of gay men and lesbian women in Spain has not meant that classrooms stop being unsafe spaces for gay and lesbian students. Teachers are key agents in this scenario, yet there are few studies that analyse and intervene in the subtle sexual prejudice of teachers toward gay and lesbian people. The aim of this study is to adapt and provide evidence for the validity and reliability of the Spanish version of the Modern Homonegativity Scale, used with trainee teachers. Method: Seven hundred and seventy-two trainee teachers at the University of Granada participated in a study with an instrument design. They provided socio-demographic information and responded to both the Modern Homonegativity Scale and two scales that measure prejudice towards trans* people. Results: The data matrix was adequate for the CFA with robust corrections for departures from normality for the two subscales, and a good fit of the data to the model was found. Cronbach's alpha, composite reliability and item homogeneity index showed evidence of good internal consistency. The AVE showed an adequate value and correlations with related con-structs were positive, significant and lower than the square root of the AVE. Finally, significant differences were found in both subscales according to religious commitment. Discussion or Conclusion: The Spanish version of the Modern Homonegativity Scale makes it possible to measure the sexual prejudice toward homosexual people of trainee teachers. It shows greater evidence of validity for the 11-indicator structural model than the 12-indicator version, with an adequate convergent and discriminant internal consistency and external validity. [Note: The issue number (62) shown on the PDF is incorrect. The correct issue number is 63.]