Leadership intelligence, professional capital, and value-based management by school principals lead to sustainable school improvement. However, the reasons for this correlation are not clearly understood. The aim of this study is to investigate the mediating role of organizational readiness in this relationship. The research is of a correlational type based on structural equation modeling. The statistical population consists of 518 elementary school principals in Urmia city. A sample of 434 principals was randomly selected using stratified sampling. Data collection tools were based on standard questionnaires for sustainable school improvement, multiple intelligences in transformational leadership, value-based management, organizational readiness, and a researcher-made questionnaire on professional capital. SPSS and PLS software were used for data analysis. The results showed that the direct effects of leadership intelligence, professional capital, and value-based management on sustainable school improvement were significant without the presence of the mediating variable (organizational readiness). This means that leadership intelligence, professional capital, and value-based management lead to sustainable school improvement even without the presence of the mediating variable. Additionally, the direct effect of organizational readiness on sustainable school improvement and the indirect effects of these variables on sustainable school improvement through organizational readiness were also significant. Therefore, organizational readiness can mediate the relationship between these variables and sustainable school improvement. These variables can positively impact sustainable school improvement by increasing organizational readiness. Hence, principals must pay attention to the role of organizational readiness to improve school sustainability by creating capacities that enhance organizational readiness.