Like other megaprojects, IS megaprojects are also large-scale, complex ventures having long duration that involve multiple stakeholders from diverse interests, are transformational in nature, and impact large population. The challenges and complexities are accentuated in the case of IS megaproject, and significantly more so in an emerging economy. In the latter case, the national context of low technology and infrastructure, institutional voids, poor governance, and higher user resistance to technology adoption are often contributory factors.The study aims at developing a conceptual model that links governance mechanisms and their influence on performance, usage, and success of IS megaproject. This is exploratory, qualitative research based on empirical evidence and uses the institutional theory framework. We have conducted 36 semi-structured interviews of the stakeholders of an IS megaproject in an emerging economy.Through the analysis of the interview transcripts and the help of relevant literature, we identified seven antecedents to the IS megaproject performance, and a conceptual model of seventeen propositions among those eight constructs, and a total of 119 scale items for the measurement of those constructs. The conceptual model explains how norms and work practices governing the project get established, and influence IS megaproject performance. This study contributes both to the empirical and the theoretical body of knowledge.