This paper develops theory and tests the relationships between knowledge management and various aspects of performance in IT-enabled business projects. The proposed theory posits that knowledge management is instrumental to Project Performance when mediated by a new concept, Knowledge Alignment. The research model is tested on survey data from 212 IT-enabled business projects. Findings show that project managers who achieve Knowledge Alignment among the people and the artefacts from three parts of the project – the IT team, the business change team, and the governance team – can have a significant positive impact on the achievement of business value from the project. Achieving higher levels of Knowledge Alignment is shown to have no significant negative impact on attainment of schedule and budget targets. This is the first statistical study to demonstrate the effect of knowledge management and Knowledge Alignment on the attainment of project management targets and of business value in IT-enabled projects.