The International Baccalaureate Diploma Programme (IBDP) is a two-year programme offered to students between the ages of 16 years and 19 years, who are in their final years of school. The students have to do six subjects-three at the high level and three at the standard level. There are three cores: Creativity, action and service (CAS), Theory of Knowledge (TOK) and an extended essay, which contribute to the uniqueness of the programme. Although the programme originated in the developed countries, there is a growing awareness regarding the programme in the developing countries. This study sets out to explore how the process of implementing the IBDP is being carried out in a private school in Kenya. The study adopted a qualitative case study design with the IBDP as the case. In order to understand the case, there was interaction with various categories of people: administrators, the IB coordinator, teachers, and students. The data was collected over a period of six weeks through observation, interviews, document analysis, and informal discussions. All the interviews were audio-recorded. Observations were recorded in a field notebook, and a reflective journal was maintained where memos and reflections were written. The study revealed that strategic planning is extremely important in implementing a new programme. It was also found that the programme is quite demanding, and the teachers and the students should be given tremendous support. The students and the teachers feel that the programme is a good preparation for higher education. However, they pointed out that they were working under pressure due to the demands of the programme. They have adopted ways of coping with the challenges. There is a good monitoring and evaluation mechanism to help in the implementation. Professional development has emerged to be very crucial in the implementation of the IBDP. However, the timetable remains a hindrance to such professional development methods; as the help of a critical friend, clinical supervision, and the guidance of mentors. The school has taken some measures to ensure institutionalization and sustainability of the programme. In order to enhance the process of implementing the IBDP in the school, the study has come up with some recommendations such as the timetable overhaul to enhance professional development, and participatory monitoring and evaluation where all the stakeholders could be involved in different ways. Suggestions for further research in the area of the IBDP have also been given.