The institutionalization of ecological civilization construction (IECC) is a process that grounds ecological civilization construction in people's ideas and actions; it promotes the combination of ecological civilization concepts, systems, actions, and effects in an institutionalized way, and promotes higher quality, greater efficiency, and improved equity in ecological civilization construction. In accordance with the logic of institutionalized operation, we construct a measurement index system to evaluate the IECC level in China from 2012 to 2022. The results show that during the study period, the IECC level exhibited a rising trend, with the institutional design and institutional efficiency index improving rapidly. The IECC level was unbalanced, showing a spatial distribution trend of being higher in the east, lower in the west, and higher in the coastal areas than in the inland areas; additionally, the absolute gap between regions gradually widened. The government's anticorruption efforts, degree of market openness, degree of public participation, and improvement in educational quality had a significant positive impact on the IECC. On the basis of our findings, we provide several policy recommendations for countries progressing toward modernization to promote the IECC.