A Power BI consultant improves data governance by implementing structured processes for data management, ensuring data accuracy, consistency, and security. They set up role-based access controls, enabling only authorized personnel to view or modify specific data sets. The consultant also establishes data lineage and documentation, making it easier to track data sources and transformations. By aligning Power BI implementation with the organization’s data governance policies, they help maintain compliance with regulations and standards, ensuring that data is handled responsibly and is reliable for decision-making purposes.