The service sector of the economy has become a major role in the economies of most nations of the world and citizens living in such economies are living in increasingly service based economies. This is because the service sector plays a dominant role in creating value in such economies and by extension, the purchasing patterns of consumers and managerial decisions of the providers of these services to a large extent are influenced by activities of players in the sector. For the service sector to maintain dominance in the economic sector, the quality of services being provided should meet or exceed customers' expectations. This research work seeks to assess the impact of the quality of banking services on the profitability of banks. To study this, we postulated three research hypotheses, relied on secondary data using the SPSS package, analysed data through the regression analysis and found out that there is no significant relationship between volume of Deposit and investment in service quality by banks in Nigeria, there is no significant relationship between investments in service quality and volume of turnover by banks and that there is no significant relationship between investments in banks' service quality and the profitability of banks in Nigeria. The absence of a clear strong relationship between service quality improvements and profitability in the Nigerian banking sector is an indication that banks are not really showing improvements in the provision of banking services that would draw the attention of customers.Based on the findings, we conclude that to be able to achieve repeat purchase by customers in the increasing competitive banking business, banks should organize their operations according to the needs expressed (or in several cases even not expressed) by their customers.