The first General Conference decided in 1946 to establish four Science Co-operation Offices in China, India, Middle East and Latin America. These offices were set up in 1947 and the network of what were later to be called “regional offices” has been extended ever since to cover all regions in the world. After 40 years of existence, in 1986, there were 27 offices of UNESCO Representatives, 2 Regional Coordinators and 23 Regional and Sub-Regional Advisers. In 2009, about 700 staff members work in UNESCO's 58 field offices around the world.

In addition to regional offices, UNESCO has helped to set up or supported otherwise numerous Centres with an international or regional character, and also centres and institutes working on the national basis, in agreement with the host country or countries or the region.
From the very beginning, UNESCO’s presence in the Field was also assured by temporary missions sent out from Headquarters or Field offices. They consisted either of a team of experts and consultants or individuals, who travelled to Member States upon their invitation to study questions in UNESCO’s competence, to work on the execution of a development project and formulate recommendations to be addressed to the Governments in the name of UNESCO.

In 1961, the Executive Board decided to designate posts of UNESCO Chiefs of Mission to be counterparts to Resident Representatives of the Technical Assistance programmes and to co-ordinate and be responsible for all UNESCO projects in a country (60 EX/Dec.9.1). In 1976, these posts were changed into UNESCO Representatives: they were usually responsible for a group of countries or a subregion. In the budget for 1981-1983 posts of “Regional Co-ordinators” were established, who were to be high-level officials responsible for a whole region. The post was tied usually with the post of the Director of a Regional Office.

Since 1951, but especially during the 1970ies, the Regional Offices were developed in a multidisciplinary direction since posts of regional or sub-regional advisors were attached to them in field which were not originally in the competence of the Office in question.

Since 1970, when the General Conference adopted a resolution on it (16 C/Res.10), decentralization became a constant subject of debate. UNESCO's decentralization policy seeks to ensure that UNESCO designs and implements programs that, although global in scope, are adapted to the needs and specific circumstances of Member States. UNESCO's Decentralization Action Plan groups Member States for service by a global network of multi-disciplinary Cluster Offices, National Offices, Regional Bureaus and Liaison Offices. The Bureau of Field Coordination is responsible for ensuring the smooth implementation of this new field network and provides a clear, single line of management.