The improvement of SISP practices has rapidly become one of the most critical issues facing many organisations, including banks. Globally, the banking sectors, including the Saudi one, have developed and implemented many IS strategies. Several systems have been executed to support the countries’ economies which have benefited from the increased trading resulting from the greater flexibility in time and costs associated with banking transactions. To continue these achievements and to improve SISP processes, several factors require careful investigation based on their relationship to SISP success; which include SISP objectives, SISP internal factors, external consultant functions, SISP external factors, measurements of SISP success, key stakeholders’ roles, and triggers. Therefore this study investigates the impact of these factors on SISP success. Data were collected in three phases. Phase 1 was an initial study with one or two interviews with the IT directors of each bank in the Saudi banking sector comprising the central bank and 11 commercial banks. The outcomes informed the development of a survey that was used in Phase 2; to investigate a sample containing a central bank, a domestic commercial bank and a domestic-foreign commercial bank to determine their SISP processes. 157 completed questionnaires were returned from the bank executives, business and IT directors and consultants. In Phase 3, 57 interviews confirmed and explained the quantitative results from Phase 2. Therefore, an in-depth case study was made in the three banks during Phases 2 and 3. The research results support previous findings on the SISP’s seventeen objectives collected by several researchers across different industries and in various countries. Furthermore, the research condenses these seventeen objectives into five more practical and achievable objectives for the banking sector. These are: 1) planning and deployment of information systems; 2) leading organisation changes; 3) improving stakeholders’ involvement and communication; 4) achieving the strategic priorities; and 5) alignment of organisational policies and architecture for business and IS. In addition, the findings identify the factors according to their relationship with SISP success and therefore explore several elements with positive, negative or no impact on SISP success in the banking sector. The thesis presents conclusions and suggests areas for further research.