National Development Financial Institutions (NDFIs) are crucial for mobilizing the required financing, including from private sources, to reach countries' climate and environmental (C and E) objectives. Funding needed to achieve countries' C and E goals is in the trillions of dollars, with many countries also facing significant fiscal and economic constraints. NDFIs are well positioned to overcome the market barriers associated with green investments and catalyze private-sector financing. The main purpose of 'Greening National Development Financial Institutions: Trends, Lessons Learned, and Ways Forward' is to examine the current trends and recommend policy actions for 'greening' NDFIs. This report identifies key steps NDFIs can take to catalyze finance toward countries' C and E objectives and manage C and E risks. The assessment of NDFIs' C and E practices is based on a review of key elements of NDFI operations and their institutional setup. The work draws from the results of a survey conducted by the World Bank of greening practices within NDFIs based in countries in a range of regions and income levels, as well as on in-depth case studies of four NDFIs: Fideicomisos Instituidos en Relación con la Agricultura, Korea Development Bank, Türkiye Sinai Kalkinma Bankasi, and Development Bank of Southern Africa.