Sustainability is becoming more important to organizations as environmental, social, and economic issues grow. This focus now extends to all sectors, including the financial one, where sustainable finance connects financial activity to sustainable development goals. Due to the extensive usage of information technology over the past decade, entering the digital economy has forced businesses to rethink their daily operations. Financial institutions are focusing on Blockchain. Blockchain technology (BC) adoption for sustainable finance is not yet well-studied. This article employs the Technology Organization Environment framework to examine through a qualitative method how BC adoption can improve financial sector sustainability. The findings of the thirty semi-structured interviews with senior managers from the financial sector in the Middle East and Turkey emphasize the role of Blockchain in sustainable finance from the TOE perspective and the need for the financial sector to integrate legitimacy practices through Blockchain to support sustainability.