Affordable housing remains a major problem for National and County Governments as the increase in population, particularly low-income earners, rises significantly annually. It is evident that despite efforts from both the national and county governments, Kiambu County still lags in the provision of affordable housing. The housing development agenda seems not to be getting the required traction at the county level with little participation by the private developers. This paper therefore, aims to establish the constraints experienced in the effective implementation of affordable housing in Kiambu County. The research design adopted in this study was survey research whereby questionnaires were used. The target population is comprised of 60 real estate developers who have an intention or have ongoing projects in Kiambu County and 100 housing officers and sub-county planners from the department of lands involved in the policy-making of affordable housing in the Kiambu County government. A sample size of 67 was adopted and a response rate of 83 per cent was achieved. The study established that the provision of affordable housing in Kiambu County is faced with various challenges such as inadequate incentives by the government, limited building technology, ineffective housing policies, inadequate supporting infrastructure, lack of access to project finance, high cost of building materials, high cost of land, and lengthy approval process. These have led to the inadequate provision of affordable housing in the county. The key recommendations of this study include; shortening the process of approving building plans and acquiring the necessary permits, making efforts towards reducing the cost of local building materials such as building stones by reducing or scraping cess fees collected from trucks transporting building materials, and the provision of adequate incentives to developers of affordable housing in the county