The devolved system of governance in Kenya has enabled County Governments to initiate various developmental-oriented projects in the counties. Most of the funds provided by the County Government are short-term and therefore do not consider funding of the project that will guarantee sustainability after funding has been withdrawn. As a result, most of these projects become abandoned or end up being a white elephant, yet a lot of money has already been spent. This study aimed to establish the determinants of sustainability of CFPs in Gatundu North Sub County in Kiambu County. The study was based on three theories, namely: stakeholders’ theory, theory of sustainability, and competence theory, all of which provided the framework of the study. The study targeted the following group of people: PMC members, project beneficiaries, the sub-county departmental heads, and chief officers’ in charge of the devolved functions. The study, therefore, targeted a total population of 100 respondents who included 30 PMC members, 50 project beneficiaries, ten head of departments and ten chief officers who in this case were engaged in the implementation of CFPs and they were, therefore, believed to possess relevant knowledge on the sustainability of the projects. The study adopted a descriptive research design. The instruments for data collection were semi-structured questionnaires and an interview guide. The semi-structured questionnaires were self-administered to the PMC members, project beneficiaries, and the sub-county departmental heads while the interview guides were scheduled for the chief officers. Questionnaires were tested to ascertain their reliability using Cronbach’s alpha with a limit of 0.6. The validity of the questionnaire was tested by use of content validity. Quantitative data were analyzed using descriptive statistics: mean, frequencies, percentages, and standard deviation. The data was analyzed using inferential statistics, which included Pearson’s Correlation analysis. Ethical considerations included the researcher seeking consent from the County Secretary and the administrative authority in Gatundu North, briefing the respondents on the purpose of the study and that information acquired would be treated with confidentiality and would remain anonymous. The study findings show that the four independent variables serve as determinants to the sustainability of county-funded projects in Gatundu North Sub-County. Project monitoring is the key determinant of county-funded projects. The government of Kiambu County, through the relevant stakeholders, should ensure that all the county-funded projects are properly monitored to ensure that they are sustainable and beneficial to the locals. Lastly, the County Government of Kiambu should focus much on hiring competent and experienced professionals to implement the projects.