Public Procurement Process (PP Process) in construction industry has identified as integral part to achieve sustainability in developing countries. Sustainability links with the social, environmental, and economic indicators. The PP Process contributes largely to the budget of developing nations. However, existing PP Processes of developing countries have shown lagging features to achieve sustainability due to a number of problems. Further, the depth and gravity of the problems depend on the impact of root causes throughout the activities and stages of procurement lifecycle of a project. Hence, this paper aims to identify the problems and related root causes during the various activities in the stages of PP Process to achieve sustainability in construction projects in developing countries. In order to achieve the aim, this study started with a comprehensive literature review to identify the stages, activities, problems and related root causes in PP Process to achieve sustainability. Subsequently, interviews with 14 subject matter experts were carried out to identify and verify the stages, activities, problems and related root causes to achieve sustainability in PP Process in developing countries. The data were analysed using manual content analysis. The findings of the study identified 10 problems and 22 root causes that affect the 39 activities in 05 stages of PP process in project procurement lifecycle in construction industry. The outcome of this paper will be beneficial to relevant authorities, funding agencies and policy makers in taking necessary steps to update the existing guidelines, bidding documents, procedures and protocols to address the identified problems and root causes to achieve sustainability of developing countries.