Positive attitudes towards inclusion of children with special educational needs (SEN) are essential for a successful implementation of inclusive education. This study aimed to test a research model comprising a series of variables that are recognized in the scientific literature for influencing attitudes towards inclusion, by means of structural equation modeling. 518 student-teachers, school teachers and principals were involved in a supra-regional online study conducted in a Swiss canton. Variables were attitudes towards inclusion, self-efficacy, attitudes towards inter-disciplinary team-teaching, experiences in specific school settings and opinions about school-environment characteristics. These were included in a theory guided structural equation model (SEM). The analyses revealed a good fit to the hypothesized model. Individual self-efficacy, attitudes towards interdisciplinary team-teaching, opinions about school-environment characteristics and practical experiences accounted for 34% of the variance in attitudes towards inclusion of children with SEN. The study allows a deeper insight in construct “attitudes towards inclusion of children with SEN” and a better understanding of the complexity of relations between the variables involved. The findings allow identifying more precisely the constellation of variables and relation-ships that play a role in predicting attitudes towards inclusion and, thus, are essential for implementing “a school for all”.