Introduction: Arrangements are made in the curriculum elements due to the individual differences of students with special needs. It is necessary to determine how programs implemented in special education classrooms are adapted by teachers for program functionality. The purpose of this study is to determine special education teachers' patterns of how and in what ways they adapt their curriculum during implementation. Method: This study, which was conducted to determine the curriculum adaptation by special education teachers and the factors that cause this adaptation, used a case study design from the qualitative research approach. The sample of this study consisted of four special education teachers: two working at the secondary level of a public school and two working at a special education and rehabilitation center. In this study, data diversification was used by employing more than one data collection instrument. These included observations, interviews, and special education lesson plans. As the data needed to be examined and analyzed in detail, content analysis was used. Findings: The observations, interviews, and document reviews revealed that teachers working in special education classrooms in public and private institutions make program adaptations such as omitting, expanding, and replacing/revising. Teacher qualifications, student characteristics, school climate, program characteristics, and family expectations played a substantial role in shaping the emergence of adaptation patterns. Discussion: Based on the results, it was found that special education teachers did not implement the written (official) program exactly in their schools and classes. It was found that the student's area and level of disability was the most important reason for the difference. The differences in the areas and degrees of disability of students with special needs in public schools and private institutions shape adaptations for expansion and revising.