The purpose of this article is to account for the relationship between expansion of areas of NGO activities and evolution of the United Nations. The theoretical novelty of this work is to identify three elements of an informal management structure of the UN and to explain the process of trans-nationalization of NGOs'activities. Empirically research is based on the results of expert's sociological survey conducted using the method of semi-structured interviews and consultations. 38 experts including leaders and employees of NGO's in consultative status with ECOSOC, UN staff and interns, diplomats, individuals acting at the UN in the personal capacity, and researchers had been interviewed in 2013-2015 and in 2016. The authors of the article conclude that consultative status was not only means for getting the international legal personality for NGO's, but also created reasons for institutionalization of whole international nongovernmental sector. The United Nations at the will of its Member States took over the function of promoting development of NGO's and provided them platforms and channels for entering the international arena. As a result, they have consolidated into a separate class of international actors. Eventually, because of the so-called boomerang effect, discovered by M. Keck and K. Sikkink, NGO's began to exert the opposite effect on the states, as well as on the United Nations itself. In particular they initiated enlargement of the sphere of UN interests, influenced so-called UN ideas, and gat linked up to the programs and projects in all activities. As a result, alongside "formal management triangle" of the UN, formed by Security Council, General Assembly and Secretariat, "informal management triangle" has been created. Its three tops are formed by: The first-by Member States, the second-by UN organs, and the third by NGO's in consultative status with ECOSOC, as well as other non-state actors. This third top in spite of its institutional weakness has significant opportunities in terms of influence on UN family in particular as a channel to provide impacts on transnational players.