ENToday, sustainability, sustainable development and clean environment come to the fore worldwide. Consequently, the concept of sustainability has been introduced in project management. Sustainability issues have gained particular attention in the real estate sector. However, despite the fact that this sector has a huge impact on the environment and society, real estate projects are most commonly chosen taking into account only their risk and return, and a very limited number of indices and methods are available to assess their sustainability. Moreover, all of the existing indices and models for assessing the sustainability of an investment project take into account only three dimensions of sustainability environmental, social and economic. Therefore, the novelty of this work lies in constructing a real estate sustainability index (RESI) relying on an additional sustainability aspect i.e., a technological dimension. The developed sustainability index could be useful in evaluating and comparing real estate projects. It would also promote technological progress and investments in new technologies within projects as sustainability is also considered in a new, technological dimension. A research study was carried out between September 2020 and December 2020. Following an analysis of the literature and different sustainability-related standards relevant for the real estate industry, sustainability criteria were chosen and then grouped into four (environmental, social, economic and technological) categories. The selection and ranking of the most relevant sustainability criteria were performed through a survey. The index was compiled by applying multi-criteria decision making methods. Keywords: sustainability; project management; real estate project; sustainability assessment; real estate sustainability index; multi-criteria decision making. [From the publication]