This article aims at analysing the financial and organizational mechanisms of the third sector, namely the non-profit organisations (NPOs) and non-governmental organisations (NGOs). In addition, it focuses on the sustainable development of non-profit and non-governmental organizations. The paper shows that in order to achieve sustainable development and embark upon the path of the “green economy”, NPOs and NGOs need to apply effective financial and organisational mechanisms that would also coincide with their regional priorities and socio-economic objectives that would take into account the environmental specifics and priorities of the given region. The article draws various examples and case studies from various countries and regions around the world to prove its points and provide some guidelines for relevant stakeholders and regulators.