Nigeria as a country operates an essentially cash-based economy in its financial transaction. This leaves Nigeria banks with the problem of having to contend with huge volume of operation and activities daily and this translates to long queues of customers in the banking hall. Managing long queues has become a major challenge for banks in the Nigeria. Queuing inefficiency have been known to have a negative influence on customer evaluations of a service environment s since a long waiting line influences customers opinion about the punctuality of a service and hence the customer’s assessments of the service provider's overall efficiency and consistency. Nonetheless the role of queuing efficiency as relating to service environment and customer behavior has not been widely discussed in literature. There is a need for this study to assess the role of service environment in moderating the relationship between queuing efficiency and customer behavior. Quantitative approach was employed using the survey. Simple random sampling techniques were adopted for this study. A total of 400 copies of questionnaire were administered to students that are customers of the four (4) commercial banks within covenant university, out of which only three hundred and eighty four (384) were retrieved and adjudged usable for the analysis. Descriptive and inferential statistical methods: Hierarchical multiple regression was used to analyse the data collected from the structured observation. The results showed significant relationships between the constructs of queuing efficiency, customer behaviour and service environment of the sampled banks however, the findings of the qualitative analysis revealed some important gaps. The results showed Service environment does not moderate the relationship between queuing efficiency and customers’ behaviour in queuing system but both service environment and queueing efficiency influences customer behaviour. Based on these findings and gaps it was recommended that in order to maintain queuing efficiency more automated teller machines can be employed in the banking premises this will facilitate higher service rate.