This study investigates the influence of Marketing Intelligence on Business Competitive Advantage: A study of Diamond Bank Plc, Nigeria. Five objectives were identified and translated into five research questions which aptly answered by subjecting them to a test of hypotheses. A Descriptive research was used to survey 292 members of the staff of Diamond Bank in Lagos, Central Regional branches and head office. Out of which 285 responses were obtained, while 6 responses were destroyed because they were not properly filled. Also, data was collected through a self-administered questionnaire, as Pearson correlation, T-test and Regression were used to test the hypotheses statements. However, the result of the findings revealed that marketing intelligence sub-constructs such as internal records, competitor’s sales data, marketplace opportunity, competitors’ threats and competitors’ risks have significant and positive influence on business competitive advantage. Thus, it can be concluded that marketing intelligence as sensitive information has enabled the bank to successfully acquire more profit, expand the branch network all over the country, perform better than its rivals in the market and increase its business competitive advantage.