With increasing investments in information technology (IT), the management and board require an IT governance (ITG) mechanism to help make decisions, mitigate risks, deliver IT values, and avoid shutdown after implementing ERP (enterprise resource planning) systems within organizations. Therefore, this research develops a holistic and enhanced ITG mechanism of an ERP system based on the Control Objectives for Information and Related Technology 5 (COBIT 5) for the post-implementation phase by adopting grounded theory and the Delphi method. This study collects 56 relevant papers published in 62 leading journals from 1998 to 2014 for constructing the prototype of an ITG mechanism of ERP systems for the post-implementation phase, and an expert questionnaire is then used to modify the prototype of the ITG mechanism. This study proposes a framework composed of 12 dimensions with 45 control items based on the governance and management areas of COBIT 5. Furthermore, this paper will validate the relationship between the ITG mechanism and organizational impact of IS-Impact Model in future. Research findings will be expected to provide a comprehensive ITG mechanism to help auditors perform effective audits by inspecting essential internal control points in post-implementation ERP systems to enhance ERP efficiency and mitigate control risk. Furthermore, this study will strive to identify an appropriate means to control an ERP system during the post-implementation phase, and to bridge the gap between ITG and ERP system success.