The system of governance in megaprojects implements a variety of companies under the consortium agreement and can affect the performance and success of the consortium. By paying attention to the literature review and results related to this issue, it is obvious that the key factors for the success of consortium are factors and components affecting governance system. The aim of this paper is to determine the impact of governance on mega multi-firm projects and its existing consequences. By using the qualitative and exploratory research method, six upstream consortiums of South Pars investigated and grounded theory used to analyze the data and find the relationships between them. The components of existing governance, as a result of process characteristics and mechanisms, as well as influential factors, identified in three categories: causative, interferential, and ruling conditions and the consequences of existing governance identified; at the end, the model of how governance influenced and its implications designed and the theory built.