This research aims to identify key factors that affect the effective implementation of the ICT master plan in developing countries. For this, the authors used a convergent mixed method which collects qualitative and quantitative data in response to research question. Based on the UN Model for strategic planning, the first part of this research compared Cameroon case with three other countries in order to identify some factors which reduce the implementation rate of the ICT master plan. Then, this study formulated a conceptual research model to include four factors(preliminary study, prioritization, communication, elaboration) from the comparative study and two factors(resources, external factors) from Heeks` model. The 126 valid data analysis results indicate that three factors(preliminary study, communication, resources) except two(prioritization, external factors) affect elaboration which impacts the implementation of ICT master plan. In final, this study provides some implications on how to successfully implement an ICT mater plan in developing countries.