In Turkey, the number of students in mainstream education is increasing, and a support service does not exist even though mainstreaming has been implemented for many years. Therefore, within this system, many students with special needs are failing. Thus, there is a need for evidence-based research projects concerning the ways of supporting these students such as the co-teaching approach. In the research detailed in this article, the participants were one regular education teacher and the researcher as special education teacher. The design of the study was action research. Data collection techniques were a checklist, documents (lesson plans, students' products), researcher journal, actual recordings of co-planning and reflection meetings and instructions. The findings were demonstrated based on the co-planning meetings, teaching practices and reflection meetings. Concerning the challenging issues of implementation, support services should certainly be provided in the mainstream classes, and additional research is needed to systematically examine the impacts of teachers taking time to undertake common planning and/or discussing student performance. (Contains 1 figure and 3 tables.)