In recent years, the significance of industrial heritage has seemed to become a growing trend
in international heritage studies. Concerning their attributed values and the crucial needs for urban development, this branch of cultural heritage has been considered the important grid of cities. This has caused a great acceptance of adaptive reuse practices especially among developing countries which is a smart response to an ongoing debate to reach sustainable development. The flexibility of these buildings and sites seems an important criterion, which can be improved through adaptive reuse practice. Therefore, this research aims to introduce the concept of flexibility in industrial heritage sites, evaluate its criteria among adaptive reuse practices, and make a comprehensive flexibility model for it. Indeed, the final goal is to determine the condition that based on the flexibility model, the adaptive reuse practice would be a proper way of encountering these sites. A historical-interpretation research method, analytical-description techniques, and questionnaire-based interviews are applied in this research. Results indicate that flexibility has genuinely been considered in this practice. Analysing flexibility techniques, this paper suggests a valuable framework to achieve the flexibility of industrial heritage as the presupposition of successful adaptive reuse in these sites.