We study the relation between the structure of financial systems and carbon emissions in a large panel of countries and industries over the period 1990-2013. We find that for given levels of economic and financial development and environmental regulation, CO2 emissions per capita are lower in economies that are relatively more equity-funded. Industry-level analysis reveals two distinct channels. First, stock markets reallocate investment towards less polluting sectors. Second, they also push carbon-intensive sectors to develop and implement greener technologies. In line with this second effect, we show that carbon-intensive sectors produce more green patents as stock markets deepen. We also document an increase in carbon emissions associated with the production of imported goods equal to around one-tenth of the reduction in domestic carbon emissions.