This study examines Portuguese teachers' attitudes towards inclusive education and how teachers' self-efficacy towards inclusion and other sociodemographic and professional variables relate and predict teachers' attitudes. In total, 539 Portuguese teachers participated. Sentiments, Attitudes and Concerns about Inclusive Education scale, Teacher Efficacy for Inclusive Practices scale and a sociodemographic questionnaire were used to collect data. The results indicate that teachers' attitudes towards inclusion were generally positive. However, teachers-related variables (e.g., teachers' self-efficacy, teaching experience, previous training, and knowledge about educational laws and policies) influence teachers' attitudes in a complex and dynamic way. Implications for policies, practices and research are presented.