In today’s world, political economics of petroleum has been an increasingly important aspect of diplomacy and political economics. The huge weight of economics and petroleum politics make it imperative part of parcel of any study to review the dynamic due as well as the influencing factors on how authorities derive to certain decisions and what are the basis of their overall considerations. This paper is examination of the complex individual influences central to the way in which decision-making is pursued, most notably from the point of view of the cognitive, normative, and psychological perspectives. The aim is by utilizing qualitative and quantitative data analysis to outline the likelihood influence of cognitive biases in decision processes as well as examine the relationships of these biases on outcomes of decision made about development of Caspian Sea oil & gas joint deposits. Subsequently, depict how to avoid the adverse impacts and risks (economic, political and social risks) in future.  The ultimate aims are to derive to a series of lessons learned, which becomes an input to improve the decision making process in future development of Caspian Sea joint field of oil and gas deposits and its resolutions. It also addresses many hidden issues behind many decisions made by Iranian decision makers regarding the development of joint fields of Caspian Sea oil and gas resources and as to how and why the political – economic related reasons for government actions usually camouflaged and rarely discussed publicly by politicians or media.