National development banks (NDBs) and development finance institutions – domestically focused, publicly owned financial institutions with a specific development mandate – are poised to play a role in bridging the investment gap for climate-compatible infrastructure in developing countries. But delivering on the Paris Agreement will require NDBs to transition from their traditional role as ‘financer’ to ‘mobiliser’ of investment for infrastructure, and to be better recognised in the international climate and development finance landscape. This paper highlights the role of NDBs drawing from case studies of the Brazilian Banco Nacional de Desenvolvimento Econômico e Social and the Development Bank of Southern Africa. As such, it provides important impetus to the international discourse on decisive climate action.