This paper examines the role of central banks in ‘greening’ financial systems. Given the enormous investments needed to bring about a green transformation, the financial sector will have to play a central role in allocating resources towards a sustainable and green economy – and stop financing activities that harm the environment. Against this backdrop, the paper examines the extent to which environmental factors impinge on central banks’ conventional goals and provides a theoretical analysis of the cases for and against central banks to respond to environmental and sustainability challenges.