The research aimed to identify the extent of the effectiveness of the environmental feasibility study in achieving environmental benefits and improvements, as well as to identify the extent of the effectiveness of the environmental feasibility study in achieving the environmental dimension of sustainable urban smart cities in Egypt, especially the New Administrative Capital. To achieve the research objectives, the “researchers" designed A questionnaire form was distributed to a sample of the research community of academic professors, faculty members specializing in environmental feasibility studies at Ain Shams University, and some environmental and urban planning experts involved in the construction of the New Administrative Capital. The “researchers" used the descriptive analytical approach to complete the study, as well as appropriate statistical tests.  To test the validity of the hypotheses and answer the questions of the study, the results of the study found that there is a positive, statistically significant relationship between the effectiveness of the environmental feasibility study and the environmental improvements achieved for sustainable urban smart cities. It also showed that there is a positive, statistically significant positive relationship between the effectiveness of the environmental feasibility study and achieving the environmental dimension. For sustainable development.