This paper examines the increasing importance of green, social and sustainable bonds in the financial markets. We first detail the theoretical framework, introducing sustainable development and green finance; relating green bonds to both ecological economics literature, and the central banks perspective; and, finally, analyzing the green bonds efficiency as a financial resource. Afterwards, we estimate the effect of green bond issues on the companies share’s price. So we collect the companies share’ prices around the announcement of the issue. Then we build an event time window with different time ranges before and after the announcement with the accumulated returns in order to be able to observe the reaction in the market in different stages. We demonstrate that the announcement of a green bond has a positive reaction in the market by increasing the return on shares of green bond issuing