The central purpose of this paper is to explore and evaluate users’ experience of service performance of four private university libraries in Bangladesh. For primary data collection, the study used a 26-item instrument based on five dimensional modified version of SERVQUAL scale. Respondents indicated their degree of opinions on a 7-point Likert-type scale in the three column format. SERVPERF scale (perceptions scores) was applied to explore the service performance. To evaluate existing service performance, the study develops a Service Performance Matrix (SPM) using SERVPERF scale. Result shows that services of IUB library at a large scale (twenty items) and EWU library at a limited scale (three items) are perceived with better performance. The other service items of these university libraries are seeking immediate improvement, which is equally implied for the whole service items of NSU and BRACU libraries. The SPM method used in this study may acts as a more comprehensive performance assessment tool for the librarians to determine the level of service performance, and to maintain the order of improvement priorities for the service items.