Multi-stakeholder initiatives (i.e., partnerships between governments, civil society, and the private sector) are an increasingly prevalent strategy promoted by multilateral, bilateral, and nongovernmental development organizations for addressing weaknesses in public sector governance. Global public sector governance MSIs seek to make national governments more transparent and accountable by setting shared standards for information disclosure and multi-stakeholder collaboration. However, research on similar interventions implemented at the national or subnational level suggests that the effectiveness of these initiatives is likely to be mediated by a variety of socio-political factors. This dissertation examines the transnational evidence base for three global public sector governance MSIs — the Extractive Industries Transparency Initiative, the Construction Sector Transparency Initiative, and the Open Government Partnership — and investigates their implementation within and across three shared national contexts — Guatemala, the Philippines, and Tanzania — in order to determine whether and how these initiatives lead to improvements in proactive transparency (i.e., discretionary release of government data), demand-driven transparency (i.e., reforms that increase access to government information upon request), and accountability (i.e., the extent to which government officials are compelled to publicly explain their actions and/or face penalties or sanction for them), as well as the extent to which they provide participating governments with an opportunity to project a public image of transparency and accountability, while maintaining questionable practices in these areas (i.e., openwashing). The evidence suggests that global public sector governance MSIs often facilitate gains in proactive transparency by national governments, but that improvements in demand-driven transparency and accountability remain relatively rare. Qualitative comparative analysis reveals that a combination of multi-stakeholder power sharing and civil society capacity is sufficient to drive improvements in proactive transparency, while the absence of visible, high-level political support is sufficient to impede such reforms. The lack of demand-driven transparency or accountability gains suggests that national-level coalitions forged by global MSIs are often too narrow to successfully advocate for broader improvements to public sector governance. Moreover, evidence for openwashing was found in one-third of cases, suggesting that national governments sometimes use global MSIs to deliberately mislead international observers and domestic stakeholders about their commitment to reform.