Co-teaching is considered a means for improving the inclusion of students with disabilities in mainstream classrooms. This research employs a mixed methods research approach to investigate teachers' attitudes towards co-teaching practices for students with disabilities in Greek schools. In total, 400 co-teachers completed a survey questionnaire and 10 of them participated in semi-structured interviews, in which they reported co-teaching practices with regard to planning and evaluation activities, co-teaching models, content of teaching and instructional grouping arrangements. The participants stated that the time they spend to plan and evaluate together is insufficient and that they need more time to perform these activities. In addition, co-teachers were found to use their limited time to separate rather than to co-plan or evaluate co-teaching activities. They reported inconsistencies in the rating of co-teaching activities during planning and evaluation. Even though co-teachers approved a specific stance towards all models of co-teaching, they mainly noted that they implemented supportive co-teaching. Also, they stated that they modify the content of teaching for their students with disabilities, but they limit this practice to individual teaching in order to assist these students to overcome specific difficulties. Finally, co-teachers indicated that they prefer to teach the students with disabilities in mixed ability groups rather than to teach them individually out of the class. The results of this research support those of previous studies with regard to the planning needs of co-teachers and the prevalence of the supportive co-teaching model. In addition, our results inform the field about diverse approaches and inconsistencies in delivering the curriculum and the grouping arrangements for students with disabilities. We argue that professional development on the practical implementation of co-teaching and administrative support are necessary to enhance co-teachers' activities towards the development of an inclusive culture.