Teachers' attitudes towards inclusive education are among the most relevant predictors of successful inclusion. Several factors related to child, teacher and environment predict teacher attitudes. This study aims to analyse the relationship between teachers' attitudes towards inclusive education, their perception of self-efficacy, and perceived school climate. A total of 463 teachers (81.4% female) participated in this study. A sociodemographic questionnaire, the Multidimensional Attitudes Towards Inclusive Education Scale (MATIES; ("International Journal of Special Education," 23, 2008, 82); Portuguese version from "European Journal of Special Needs Education," 31, 2016, 111), the Teacher Efficacy for Inclusive Practices (TEIP; ("Journal of Research in Special Educational Needs," 12, 2012, 12); Portuguese version from Ensaio, 25, 2017, 7), the School level Environment questionnaire climate questionnaire (R-SLEQ; "Educational and Psychological Measurement," 67, 2007, 833; translated by researchers) were used. Results showed that participant teachers possess positive attitudes, although moderate, towards inclusive education. In addition, findings suggested a significant positive relationship between self-efficacy, school climate and teachers' attitudes. Self-efficacy mediates the relationship between school climate and teachers' attitudes regarding inclusive education. Implications for teachers' training and collaborative practices are discussed.