The Organization for Economic Development and Cooperation (OECD) has started with its work in the 1960s. Initial it counted 18 countries, today there are 36 member states. Apart from economic cooperation, this organization also has an important impact on the work of other, similar international institutions, improving partnership with them and encouraging their work. Significance and impact is also visible in the implementation of some OECD proposals on the legislative frameworks of the European Union and the legal acts that are in force in the EU member states. OECD specifically promotes tax diplomacy that is the subject of this paper. It is not a new form of diplomacy, but it is clearly implemented and visible through the work of the organization. From historical perspective and todays trend, tax are the most important form of financing modern countries, and by cooperation between countries and membership in the OECD, they create a more transparent, efficient and uniform tax system, avoiding tax evasion. As a result, economic development, tax morale growth, and central government budget are filling more.