School leaders have an important role in supporting implementation of inclusive education practices in schools. Therefore, it is necessary to understand how school leaders' attitudes towards inclusive education are formed. We used the Attitudes Toward Inclusive Education Scale that was developed to measure different facets of attitudes towards inclusive education "for all" students. The instrument was completed by 301 school leaders in Estonia. Three factors describing attitudes in facets of inclusive education practices, vision, and supports were distinguished. Structural Equation Modelling revealed that school leaders' practices towards implementing inclusive education approaches are driven more strongly by their vision than the support available to them, although both aspects have a significant effect on their attitudes towards these practices. However, participation in in-service courses focusing on inclusive education and working as a school leader in a special school had negative association with school leaders' attitudes towards inclusive education practices.