Urban and rural perimeters are boundaries that outline urban and rural areas. The delimitations of these areas are established according to a set of criteria supported in detailed baseline information such as resident population, the existing infrastructure, and the existence of public facilities. However, in situations where all the basic information needed to enable the current method of delimitation is not available or suitable, the planning process can be compromised. In these situations, it is necessary to create an alternative method that enables the delimitation of urban and rural perimeters in order to establish development conditions according to these perimeters and ensure the promotion of a correct and efficient transformation of the territory. This paper presents and discusses the method developed for the delimitation of urban and rural perimeters in the regional plan for Oé-Cusse Ambeno in Timor-Leste [Plano Director de Ordenamento Territorial da Região Administrativa Especial de Oé-Cusse Amben (PDOT)], supporting the elaboration of this plan by the Special Administrative Region of Oé-Cusse Ambeno. This method was developed specifically to enable the delimitation of urban perimeters in a context where the most basic baseline information is lacking, a characteristic situation in the majority of developing countries. In order to carry out the planning process, the method developed integrates a set of criteria from which it identifies the most determinant criteria to allow the establishment of a hierarchy of existing clusters (settlements) and the delimitation of the urban and rural perimeters. This activity has made use of a group of experts from the fields of architecture, territorial planning, geography, environmental sciences, landscape architecture, civil engineering, economics, and the law, all disciplines required to inform the applicability and weighting of each criteria. The result of the developed method has been applied in the conception of the PDOT in which the minimum baseline information to conduct future planning practices has been put in place. The conclusions show that the method applied provides an efficient delimitation of the urban and rural perimeters, which was validated on the PDOT framework and is able to be integrated into future plans.