Resources are scarce. Public and private entities must ensure that available resources are allocated efficiently and utilized for the intended purposes in order to achieve strategic objectives. In Kenya, the principles of public finance are enshrined both in the constitutions and various legislations, the most important of which is the Public Finance Management Act. While both National and County governments are expected under law and by the citizenry to pursue optimal financial performance, reports on budget implementation show mixed results. The Auditor-General Report on Elgeyo Marakwet has consistently indicated suboptimal budget absorption rate and poor financial performance, which raises questions about the effectiveness of budget implementation in the County government. This study investigated the effect of budget implementation on financial performance of Elgeyo Marakwet County. The specific objectives were: to establish the relationship between budget planning, budgetary staff capacity, financial resource availability and audit processes on the financial performance of Elgeyo Marakwet County Governments in Kenya. This study was grounded on three theories: the theory of public finance, the budget theory, and the decentralization theory. A descriptive research design was used to guide the investigation of the stated objectives. The target population for this study were the accounting officers at Elgeyo Marakwet County. A census sample of the 79 accounting officers was used in the study. Primary data was collected using standardized and validated questionnaires, administered through a drop and pick method. SPSS version 23 was used to analyze the data. Descriptive statistical techniques were used to compute the percentages, means and standard deviations. The inferential measures; Pearson Correlation and Linear regression, were used to determine the relationship between the independent variables (budget planning, budgetary staff capacity, financial resource availability, and audit processes) on the dependent variable (financial performance) of Elgeyo Marakwet County. The descriptive statistics indicate very high level of agreement with statements concerning budget planning, budgetary staff capacity, financial resource availability, audit processes and financial performance at the County. Correlation and regression analysis showed that while some processes had a positive effect on performance. The regression statistics indicate that there is a positive and statistically significant influence of budget planning, financial resource availability, budgetary staff capacity, and audit processes on financial performance. The study recommends continuous strengthening of budget planning processes, greater investment in the human resource capacity, efficient allocation of financial resources to the budgeting process, and strengthening of existing audit controls and oversight systems in order to achieve higher levels of transparency, accountability, efficiency, and financial performance.