The Puerto Princesa Underground River (PPUR) is managed by the City Government of Puerto Princesa based on a program centered on environmental conservation and sustainable development. It has the distinction of being the first national park devolved and successfully managed by a Local Government Unit. It is a designated core area for the Palawan Biosphere Reserve under the Man and Biosphere Program. It is inscribed by UNESCO as a World Heritage Site since 1999. Utilizing a survey, this research aims to determine the knowledge, attitude, and practices of tourists towards the Puerto Princesa Underground River. Findings showed that tourists are knowledgeable about the PPUR, including the basic facts about it. However, not all tourists are aware of its history. Although tourists do not know some facts about it, they still tend to go and visit the place because of its natural beauty and its inclusion in the World’s New Seven Wonders of Nature which boosted its appeal as one with Puerto Princesa, in particular and Palawan, in general. In line with getting a positive result for the attitude of the tourists towards the Puerto Princesa Underground River, their practices also showed a positive approach. This findings show that although the tourists often read articles and visit PPUR, they would still follow the rules and regulations within the PPUR premises to preserve its beauty and its resources. One reason why tourists want to preserve the PPUR is for others to have an opportunity to visit and see it. As for the correlation of the three variables, knowledge and attitude are not related to each other and so as knowledge and practice, and attitude and practice.