Post-adoptive usage behaviors of information systems (IS) are critical for a firm to successfully improve performance and sustain competitive advantages. As a form of post-adoptive usage, extended use is conscious behavior beyond routine that requires the extra involvement of users’ time and efforts. Drawing upon the insights from the IS continuance model and organizational commitment theory, we developed a research model to investigate the role of user commitment in extended use of IS in this study. With the survey of 240 ERP users, our results indicated the important basis of IS continuance model for understanding post-adoptive extended use. We also found the different roles of commitment factors in explaining extended use. Specifically affective commitment influences extended use via user satisfaction; while continuous commitment has a direct effect on extended use. This study highlights that the integration of user commitment factors with IS continuance model contributes to better understanding post-adoptive extended use.