Nowadays, marketing strategies have undergone many changes in the banking industry. In the past, the main goal of senior managers of banks was to attract new customers and to provide a variety of products to them, while banks are looking for creating and maintaining the profitable and long-term relationships with loyal customers nowadays. Customer retention provides the conditions for continuous growth and development of banks. Maintaining and strengthening the customer loyalty and preventing from customer withdrawal are considered as strategic challenge for banks, which are concerned on development of their competitive status. Effort to investigate the causes of the key customers’ withdrawal is the challenge that banks grapple with it in today's competitive environment. Therefore, the main issue in this study is to find that what factors lead withdrawal of customers of a bank. The aim of this study is to explore and achieve deep understanding of the causes of customers’ withdrawal of receiving banking services of a bank. This study is a qualitative research in terms of nature of the data. By juxtaposing the findings of various researchers and combining them, we conducted a descriptive study. Exploring the reasons of customers’ withdrawal of a bank would help banks retain their key customers better than before and allocate their limited resources in the best manner.