Employee retention is mostly influenced by good leadership, career development; free communication, compensation and promotion at work The same reasons applies to the bank employees since employee retention causes don‟t differ much from those of the banking industry. The effect of employee retention involves low organizational performance, loss of experienced employees, high administrative hiring cost and shifting of customers to other banks. The study aimed at investigating on the role of organizational culture on employee retention in banking, a case of Tanzania Postal Bank, Mwanza- Tanzania. Where there is a decreasing number of employees at TPB which contributed much on conducting this study. The objectives of this study were to find out the effect of organizational culture on employee retention, to examine on the perception of the employees on organization culture towards employee retention and to identify on the possible strategies used by the organization to promote retention. The sample size of the research was 50 which involved TPB employees and the branch managers. Research data were collected using questionnaires that were distributed to TPB employees and interviews were conducted to TPB branch managers. The researcher used both qualitative and quantitative approach in analyzing the data. Tables were used to summarize the data provided. The study found out that among the causes of employee retention at TPB were insufficient salaries, lack of employee‟s benefits and lack of opportunity for advancement. The strategies that TPB use to retain its employees were providing bonuses and rewards as a motivation to the best employee of the year, training employees to be loyal to the bank and committed to their work. The study recommends that the bank should provide employees with rewards so as to boost the employees performance and increase the organizations productivity, also the management should give employees a chance to express their problems concerning the organization and lastly the management should assess their employee retention strategies at least once a year, so as to keep the employees morale high and turnover low while guaranteeing your organization success.