This qualitative study is aimed at describing the implementation of the Malaysian Physical Education school curriculum in Form One in schools. The focus of the study is on the role of teachers in implementing the curriculum according to what is planned (fidelity perspective) and the factors influencing the teachers in adapting the curriculum (adaptation perspective). Respondents were two teachers who taught in the vicinity of the Klang Valley. Data were gathered through interviews with the teachers, observations of teaching and learning over seven months, and related curriculum documents. Findings showed that although teachers outwardly, that is, in their lesson planning book implemented according to the curriculum documents, in practice what actually transpired in the Physical Education class was the opposite. In other words, the formal or written curriculum differed from the implemented curriculum experienced by the students. This gap in implementation depended on factors such as interest, requirements and needs, and gender of student, infrastructure and facilities available, as well as the teacher's conceptions regarding the importance of Physical Education and their role related to it. Hence, it can be concluded that Physical Education teachers have wide scope to adapt the curriculum because the status of the curriculum is not examined. The findings give the implication that curriculum planning of Physical Education must take into account the unique characteristics of the subject because only by doing so can the pure objectives of the curriculum be achived, namely the aim of ensuring students attain fitness through physical activity and practising good habits.