Abstract: Infrastructure projects plays a big role in societies in terms of meeting the development needs of the economy and more so in transforming the quality of life of citizens. The government is the single largest implementer of public infrastructure projects thus there is need to ensure that these projects are fully implemented and the factors that have the greatest influence identified to ensure their influence is taken into consideration during the project life cycle. It was therefore the purpose of this study to investigate the critical factors influencing the implementation of public infrastructure projects in Kenya, a case of thika-sub county in Kiambu Kenya.