The present study aims to evaluate the quality of services provided in library of faculty of Psychology and Education in Allame Tabatabaee University and identification of those service components in this library which require promotion and improvement. In this study, LibQUAL^TM (final version) has been utilized. Using this tool, service quality is determined by evaluation of the existing gap between “minimum acceptance level” and “perceived level”, and also the gap between “maximum acceptance level” and “perceived level”. This indicates the significant difference between the levels, as well as weaknesses and strengths of a library. The current research has been carried out using survey method. Sampling method has been cluster random sampling technique and among library clients 346 persons have been chosen as samples. Results of the study indicate that, the library has been able to satisfy the minimum acceptance level of clients in the component “effect of service”. Nevertheless, the library did not facilitate to satisfy this level in the components “information control” and “library as a place”. Following the hypotheses testing in each of LibQUAL components, the researchers found out that a significant difference exists in all the three components between the “perceived level” and “minimum acceptance level”, as well as between the “perceived level” and “maximum acceptance level” concerning service quality. Furthermore, it was specified that from clients’ viewpoint, the component of “information control” is of higher significance compared to other components.