While previous studies have paid a lot of attention on ERP implementation, this study aims to investigate ERP post-implementation success. The need of the investigation emerges to be critical due to the ever-increasing challenges, from ERP system itself and from ERP service team, in this phase. We assess relative importance of IS quality (system quality and information quality) and service quality on post-implementation success from the perspective of users, which includes users’ continuance intention to use, satisfaction, and performance. Our research model was empirically examined by using a sample of 151 current ERP users in manufacturing sector. The results have revealed that: (1) Service quality is less influencing to ERP post-implementation success than IS quality; however, service quality is the one that has the strongest impact on user satisfaction. (2) More specifically, six of the nine quality constructs-contextual quality, system-related quality, task-related quality, assurance, empathy, and tangibility show influencing, while the other three-representational quality, reliability and responsiveness fail to show significant contribution to post-implementation success. (3) The influencing quality factors do not necessary lead to the same effect on the categories under the post-implementation success, implying they play different role in facilitating conditional success. (4) Of all the quality factors, contextual information quality appears to be the most critical one on ERP post-implementation success, indicating that ERP vendors and ERP service teams should pay more attention to minimize users’ concern in this dimension.