The aim of this study is to explore the CELTA course from the perspective of EFL instructors. A single case study of qualitative research methods is employed in the study. The sample consists of 6 EFL instructors working for a private university in Turkey. The quantitative data of the research was obtained through course evaluation survey. Qualitative data was gathered by open-ended questions and interview forms developed by the researcher and also with the documents. Descriptive analysis was performed to show evaluation of the course in the quantitative phase of the research. On the other hand, the content analysis method was applied in the analysis of qualitative data. As a result of the study, the CELTA course is useful for EFL instructors' careers; nevertheless the course components and content should be redesigned considering andragogic principles. Moreover, EFL instructors were pleased to take the course at the end of the course although the course's weaknesses.