As a consequence of the continuous increase in the importance of Information Technology as a critical component of an organization's day-to-day operations and its strategic capabilities, organizations have raised their concern to establish and implement mature and effective IT Governance. Using data from 20 organizations within financial services, telecommunications, manufacturing, and public service, this paper focuses on identifying the most influential IT governance domain for increasing the level of IT governance maturity and identifying the most influential IT governance mechanism for increasing the overall effectiveness of IT governance. Using Partial Least Squares (PLS) Path Modeling, this study found robust empirical evidence that the most influential IT governance domain is Monitoring of IT Performance Measurement and the most influential IT governance mechanism is the implementation of Corporate Communication Systems.