At ministry assembly in Budapest in March 2011, republics such as Austria, Slovenia, Hungary, Croatia and Serbia, were signatories of common Declaration on the preparation of the establishment of the ”Mura - Drava - Danube Transboundary Biosphere Reserve”(MDD-TBR). Even though this document does not have obligatory character for states that signed it, this declaration represents the obvious course these states will follow in order to improve their cooperation. Beside political, economic, cultural and other well developed forms of cooperation, a multilateral cooperation emerges within the areas of conservation, protection and improvement of flora and fauna of the Danube and rivers Drava and Mura that belong to The Danube River Basin. In this article the author provided a short review of basic international legal documents that refer to Biosphere Reserves regarding specifically the overall Danube Strategy by European Union and belonging Action Plane to Danube Strategy. The author analyzed the paramount clauses of Declaration MDD - TBR, with intention to reveal this little known document to scientific and professional public. In that sense, the principles for selecting the actual biosphere reserve have become a priority as well as the elemental objectives a biosphere reserve should accomplish and its spatial organization.