A Dissertation submitted in partial Fulfillment of the Requirements for Award of the Degree of Master of Business Administration-Corporate Management (MBA- CM) of Mzumbe University. Morogoro, Tanzania.The study mainly assessed the factors leading to customer mobility among commercial banks in Tanzania using selected National Bank of Commerce Limited as a case study. The specific objectives included to identify factors that make customers to shift from NBC Ltd to other banks; and to determine strategies that the bank can use to retain its customers. The sample size of the study was 80 respondents. The research tools used were questionnaires, interviews and documentary reviews. The study found the major factors for customer mobility in NBC were based on dissatisfaction in high interest rates charged for loans; low interest rates on savings; Islamic banking; unpromising services; rude staff and management; insufficient promotion and marketing strategies; and inaccessibility of NBC branches. The study also found that to retain customers, NBC needs to increase the number of employees; to increase the number of bank branches especially in the district towns; to effectively motivate the employees; and to improve services to the customers. It was also found that the impacts of customers shift to other banks were unmet NBC objectives; increased institutional administrative costs in NBC; and reduced institutional competitive advantage in NBC. The study concludes that the factors responsible for the customer shift from NBC to other banks were external and internal. However, the major factors were factors that need to be controlled by the bank itself in order to increase its performance and competitive advantage in the banking industry. The study also concludes that impact of the customer shift from NBC to other bank was a negative aspect that would lead to decreased performance, productivity, lessened competitive advantage and unfavorable corporate positioning in the banking industry. The study also concludes that the bank management needs to take action early by improving working banking environment, working conditions and services in order to retain old customers and to attract new ones.