The project implementation schedule is an important plan for every construction project, to reduce and control project delays. The implementation of urban development investment projects is increasing in terms of both quality and quantity as urban areas are rapidly developing in cities. However, many construction projects are scheduled but they are late from due time. As the number of urban development investment projects increases, understanding the causes of project delays will help project managers and stakeholders limit these delays. This paper investigates all those factors which are causing a delay in the development of urban investment projects These factors are further developed through expert knowledge elicitation using the Delphi method. Lastly, as based on the issues identified were run to determine how they affected project delays. Finally, a survey based on the issues identified factors was conducted to assess how they affected project delays. The linear regression model is used to analyze the results from the survey. The results of the study indicate that there are six main factors that cause the delay in the implementation of urban development investment projects in Vietnam, including Policy, Design, Cooperation, Implementation, Financing and Objective factors. The study's findings indicate that there are six primary groups of elements, including Policy, Design, Collaboration, Implementation, Finance, and Objective factors, that contribute to the delay in the execution of urban development investment projects in Vietnam. The study offers a research model for the factors that contribute to delays in the execution of construction projects for urban development. This finding can serve as a foundation for ideas on how to deal with this issue in Vietnam as well as a guide for similar works.