Criteria and indicators for national park assessment are tools for supervising the stability of national parks, which yet should be include high environmental, economic and social standards. The purpose of this study is to identify and customize ecological, economical and sociopolitical criteria and indicators for sustainable management of the national parks in Iran. In this study, ­ views from 36 environmental experts and professionals in sectors relevant to national parks management were collected in a four-step process by means of questionnaires, followed by data analysis by Delphi method applying a set of criteria and indicators of IUCN, CIFOR and other sources. The experts were asked to express their views on the importance of criteria and indicators based on Likert scale. The results were summarized, which all in all resulted in 8 criteria and 142 indices. The fourth analysis step, 100 final indices out of initial 142 were agreed on. The criteria include extent of forest resources, conservation of biological diversity, Health, vitality and integrity, productive capacity and functions, protective and environmental functions, maintenance and development of economic functions and conditions, maintenance and development of social functions and the legal and institutional frameworks. The number of indices was 67, 15, 7 and 11 for ecological, social, economic and political aspects, respectively. The results revealed the highest number of indicators to be related to ecological aspects, while the economic aspect embraced the least indicators. The results suggest the Delphi method as a useful approach to identify and localize the criteria and indicators, which enable Department of Environment to monitor the stability of ecosystems within the national parks.