The construction sector is a key player for sustainable development. Both levels of government in Kenya (National and County) have identified the construction sector as a driver of the development agenda. The devolved units (counties and constituencies) have invested quite a substantial amount of public funds in infrastructure development and yet social audit and media reports have raised the concern over the poor quality of the projects undertaken by these devolved units. This study, therefore, sought to investigate the project management process to determine its effects on the quality of public building projects. A case involving sixty-four projects sampled from Busia County and its seven constituencies was carried out. The study was a sample survey whose data was collected using questionnaires, interviews and physical observation exercise. The data were analyzed using descriptive statistics and Chi-square good-for-fit tests. The findings indicated the very low participation of the public works officers as project managers in the construction process of the public building projects undertaken by devolved units. The participation rate was at 15% which implied that the projects were constructed without a professional project management process. The physical observation assessment revealed the quality of the public building projects stood at 34% compliance to building specifications and standards which is inadequate to meet the required standards. It is concluded that the involvement of public works officers as project managers in the construction management process of public building projects undertaken by the devolved units was inadequate and impacts negatively on the quality of the projects. In order to achieve the sustainable development as far as the infrastructural development is concerned, the involvement of professional project managers in the construction process was critical. This, therefore, called for the development of the legal and quality frameworks to guide the construction sector at the devolved units.