The tourism is an industry that makes extensive use of natural heritage sites. It has long been debated whether tourism is a threat to natural heritage sites. This research has been written to contribute to these discussions. In the study, the author(s) aims to determine the effects and threat levels of tourism in World Natural Heritage Sites. Within the scope of the research, the impact of tourism on 24 samples selected from UNESCO natural heritage sites was examined with multi-criteria decision-making methods. According to the results of the research, the highest endangerment level among the selected NHS are "Lake Malawi National Park", "Machu Picchu Historic Sanctuary" and "Phong Nha-Ke Bang National Park", while "Atlantic Forest Southeast Reserves", "Sinharaja Forest Conservation Area" and "Vredefort Dome" were found to be the least affected sites. The research results were discussed with the implications developed in accordance with the contexts of the selected NHS.