This study examined the impact of Management Information System (MIS) on organizational performance, using First City Monument Bank (FCMB) Plc branches in Osun State, Nigeria, as the focus. Specifically, the study investigated the effects of Automated Teller Machine (ATM) usage, Short Message Service (SMS) operational activity, and Bank Verification Number (BVN) effectiveness on organizational performance. Relevant theoretical and empirical literature on MIS and organizational performance was reviewed, while Innovation Diffusion Theory (IDT) and Socio-Technical Systems Theory of Acceptance were adopted as the underpinning theories. The study employed a survey research design, with primary data collected through a structured questionnaire. The population comprised 72,885 customers of selected FCMB branches in Osun State, from which a sample size of 399 was determined using the Taro Yamane formula. Data collected were analyzed using descriptive statistics and regression analysis. The findings revealed significant positive relationships between ATM usage and organizational performance (r = .398, p < .01), SMS operational activity and organizational performance (r = .369, p < .01), and BVN effectiveness and organizational performance (r = .432, p < .01). The study concluded that MIS significantly contributes to organizational performance in FCMB Plc. It therefore recommended continuous upgrading of MIS infrastructure and the effective deployment of ATM, SMS, and BVN technologies to improve service delivery, operational efficiency, customer satisfaction, and overall organizational performance. Key words: Customer Satisfaction, Decision-Making, Management Information System; Organizational Performance, Operational Efficiency.