Current cities, especially megacities, are going through a continuous increase in population size because the city extends beyond its urban borders, causing what is called urban sprawl, which constitutes the real problem for cities at present. Also, these megacities have many informal areas and urban dilapidated areas because of the ancient period since their establishment, from which the city has suffered greatly. Hence, the need to determine development methods that should be within the city instead of expanding outside its borders, and many methods have been reached that can be used to solve this problem, the most important of which is infill development. The research methodology focused on reviewing the literature of the study and discussing the best international practices to arrive at a first draft of a list of key success factors for infill development projects and reviewing it with a group of experts who developed it until the final approved version was reached. The result of these procedures was to arrive at a conceptual framework for the key success factors for infill development. This conceptual framework applies to any city to ensure that infill development projects are successful with the highest possible quality and reflect positively on the city and its residents.