A metropolitan Region of the Third World countries like Tehran metropolitan region (TMR) in Iran, in consequence of unbalanced rapid urban growth, is facing with large set of unique social and demographic, cultural, economic, ecological, environmental and managerial problems. The entire problems are because of lack of effective regional plan and uncoordinated structure of the local authorities in concern to regional issues. Recently governments proposed a regional plan for the TMR which intends a polycentric development for the spatial configuration of the TMR. However, having the monocentric picture of the TMR in mind, this question rise that is it really possible to consider the TMR a polycentric urban region? What is the suitable regional strategy that provides synergy in the TMR? In this thesis prominent literatures related to the Polycentric Urban Region (PUR) are reviewed. Two complimentary aspects of polycentricity namely, morphology and functional relationship are identified as essential elements for polycentric development. Governance structure of region is also considered as a third element for reaping the alleged benefits of polycentricity. These three factors together formed the analytical dimension of polycentricity. These three elements were studied in the TMR context and potential and deficiency of the region regarding to these elements are identified. The normative dimension of polycentricity is dedicated to reviewing the history of the region and studying the government’s plans in course of history to see how their plans promote or discourage the polycentric structure in the region. Based on the findings it is concluded that the government’s plan for polycentric development of the region is ambitious and is not consistent with the current realities of the region. Therefore according to the analysis of the region a planning guideline in 5 aspects of centrality, mobility, low income settlements, land escape and governance is proposed. These sets of recommendations aim to provide balance development in the region and create social cohesion. Also by optimal alternation of the governments plan the TMR triangle is introduced and designed. Tehran, Karaj and International Imam Khomeini airport (IKIA) form the corners of this triangle. Three corridors connecting the three corners of this triangle is designed through Transit oriented Development. The superiority of this proposal to the government’s proposal is, first it is based on the realities and potential of the region. Second, It also considers the regional administrative organization for coordination of local authorities. The proposed plan by taking advantage of the potentials in the region steers the government’s plan to the direction which is more feasible. The proposed plan leads to more urban cohesion and synergy in the region and improve the life quality of its residents. In this thesis all the steps from literature review to planning, design and evaluation of the plan are explained extensively.