This study aims to determine the level of fidelity of preschool teachers to the curriculum within the framework of school-based practices (SBPs) and evaluated in terms of participant responsiveness. In this case study, interview and document analysis methods were used to collect the data from eight preschool teachers working in a university kindergarten. Results indicate that the teachers were attempting to implement the school-based curriculum development (SBCD) approach, but with a limited understanding. The findings reveal that teachers who adopt the adaptation approach structurally adhere to the curriculum, and their process fidelity is extended in SBPs. It is also concluded that the supportive educational environment, participatory institutional culture, teacher qualifications and the curriculum structure promoting flexibility in practice contribute to fidelity.