Background: Most countries have started to educate students with special educational needs (SEN) in mainstream schools, but it remains unclear how inclusive attitudes towards students with SEN can be promoted. Aims: This study investigated the role of adolescents' friendships and socio-moral competencies for their attitudes towards the inclusion of students with SEN. Specifically, we studied whether adolescents without SEN would develop more inclusive attitudes if they had close friendships with SEN students and if they expressed negative emotions about social exclusion. Methods: Adolescents' inclusive attitudes and their emotions were gathered from survey data of 1225 Swiss students aged 11-13. Social network data were collected to assess adolescents' friendship relationships. Results: The results indicated that adolescents' friendship closeness with SEN students positively related to their inclusive attitudes. However, this was only true for adolescents who anticipated more negative than positive emotions if a student with SEN was excluded. Implications: These findings highlight the role of friendship relationships between adolescents with and without SEN and adolescents' socio-moral experiences for their attitudes towards the inclusion of peers with SEN. Thus, inclusive education may benefit from promoting friendships among students with and without SEN as well as adolescents' sociomoral competencies. (C) 2017 Elsevier Ltd. All rights reserved.