The objective of this study was to establish the factors influencing successful implementation of core banking system. The specific objectives for the study were: To find out the processes involved in implementation of a Core Banking Systems (CBS), to identify the factors influencing the successful implementation of CBS and to design a framework that will be used for implementation of CBS. The study adopted descriptive survey and targeted 374 members of various banks as the sample frame. Quantitative research methods and techniques were applied by the researcher in undertaking the research. The research instrument for the study was questionnaires being the primary data collection tool. The data collected was analysed using SPSS (Vs21). The data was manipulated through descriptive statistics such as percentages, range, mean scores and regression analysis. The presentation of data was through tables and graphs. From the findings the study concludes that all the independent variables; Initial Systems Requirements and Analysis, Project Management and Vendor, Software and Hardware selection had a positive and statistically significant correlation with the dependent variable that is Successful Implementation of the Core Banking System. The study also established that the factors critical in the successful development of a new core banking included; System requirement planning process of the CBS before implementation; End-users of the system involved in determining CBS requirements; Budget provision for the system change-over and related activities including Training and Hardware being provided; Studying old system and documenting its features for further analysis; Having an all rounded model of the system being tested; and All users requirements being taken care of in the design and modelling of the proposed CBS system. The study also revealed that team building, and skills development activities were necessary for successful CBS development. Top management support as a determinant of CBS change-over phase; Top management consistently providing all the tools and resources required to successfully deliver all the approved IT projects; Conducting efficient User Acceptance Tests before theGo-Live date and User Training was key for efficient and smooth system change-over. Vendor, Software and Hardware selection processes and final adoption was key to successful development of core banking as well as having a hardware vendor with good support. The study undertook and analyzed the responses of a total of 315 bank employees from 22 banks in various key departments.