Reference services are services rendered to students by a library in order to provide information resources for its teeming users. This study examined the perception of postgraduate students on the reference service of Kashim Ibrahim Library of Ahmadu Bello University, Zaria. For the purpose of this study, four research questions and four research objectives were postulated. Qualitative research design was used to gather data necessary to answer the research questions. Convenience purposive sampling was used to select the seven (7) interviewees from three faculties. An inductive approach was done with the aid of Nvivo software which yielded one hundred and twenty codes, seven major categories and three sub-categories. The findings from the study revealed amongst others that some postgraduate students saw the library as being adequate on first glance and hence want to come back and visit the library as they attributed to their serenity, quiet, calm and spacious and big nature of the libraries. It was concluded that approachability, interest, listening, accuracy, search and follow-up which are constructs of Durrance?s theory are very important in the information service unit as it will either encourage or discourage the user from making use of the information service unit of the libraries. It was recommended amongst others that sitting arrangements, lighting systems and unavailable/insufficient internet service ports should be improved upon.