Agency costs result from a principal-agent relationship's conflicting interests. The relationship develops because the principal may not be able to manage the business since they are technologically illiterate, numerous, and geographically spread; as a result, they hire the agent. In a commercial bank, there are various relationships that show principal agent relationships, with the most prevalent one being the link between the shareholders and the management. Agency fees are paid with the intention of aligning the agents' and principal's ambitions in order to realize the principal's overarching intentions. Therefore, the perseverance of this study was to analyze agency costs and their effects on financial performance. In this study, the agency cost on financial performance of public commercial banks was analyzed. Specific objectives were; to establish how monitoring cost affect the financial performance of quoted commercial banks in Mombasa County, to assess the effect of bonding cost on financial performance of listed commercial banks in Mombasa county, to examine the extent to which residual loss affect the financial performance of commercial banks in Mombasa county and to determine the effects of restructuring cost on financial performance of listed commercial banks in Mombasa County- directed the study. Theories supporting this study were as follows; agency theories, free cash flow and stakeholder’s theory. Descriptive design is a kind of research methodology which establishes the connection between variables. It was used in this study to identify both the broad and the detailed study goals. A census of the 10 listed commercial banks in Mombasa County was conducted as part of the work and purposive sampling was be used. This study used qualitative and quantitative methods. Validity was tested through interview while reliability was tested using Cronbach alpha. The data was analyzed using inferential statistics like regression and correlation and descriptive statistics like mean and standard deviation using the Statistical Package for Social Science (SPSS) Version 22.0. The results were presented using cross tabulation, frequency tables, and charts. Findings indicated that there was a significant impact between; monitoring cost, bonding cost and residual cost and the financial performance. Restructuring cost were determined to have a favourable impact on financial performance. Therefore, the study recommends implementing an efficient internal control system by listed commercial bank management. This will assist in cutting down on the cost of auditing, administrative costs, and wasteful and unneeded spending, Managers should be paid more and attaching monetary or share bonuses or option entitlements to particular firm performance and to adopt a type of restructuring that will align with the relevant strategy and objectives.