This study examined the effect of competitive intelligence strategy on marketing performance of selected deposit money banks in South-South, Nigeria, Specifically; two branches First Bank of Nigeria plc, UBA Plc and Zenith Bank plc in Delta, Edo and Rivers States, in South-South, Nigeria. The specific objectives of the study are to ascertain effect of the measures of competitive intelligence strategy, namely; customer intelligence (CUI), human intelligence network (HIN), technological intelligence (THI) and strategic intelligence (STI) on Marketing Performance (MKTP). Cross-Sectional Survey research design method was adopted in this study. Stratified random sampling technique was used in the study. The responses from the respondents were collected with the aid of five (5) likert scale questionnaire. Out of the two hundred and sixty-seven (267) copies of questionnaire administered two hundred and sixty (260)95.23% where retrieved and properly filled while seven (13)4.76% were not properly fill and returned. The questionnaire was coded with the aid of excel spread sheet, the respondents profile was analyzed with manual simple percentage, descriptive statistics and correlation matrix. The hypotheses of the study were tested using the multiple regression statistical tools with the aid of SPSS version 23. The findings revealed that; there is significant positive relationship between CUI and MKTP (0.035<0.001), there was a significant positive relationship between HIN and MKTP (0.001<0.05), there was a significant positive relationship between THI and MKTP (0.024<0.05) and STI had a positive and significant relationship with MKTP which is evident with the p-value (0.002<0.05). Based on the findings, the study concluded that, competitive intelligence strategy had a positive and significant effect on marketing performance in selected deposit money banks in Delta, Edo and Rivers States, in South-South, Nigeria. The study recommended that banks should invest in robust customer intelligence systems to collect and analyze customer data. This will enable them to better understand customer preferences, behaviors, and needs, leading to personalized marketing strategies that can enhance customer satisfaction and loyalty