This paper describes some ecological problems in Karimunjawa, an island in Java, Indonesia, as the possible impact of tourism activity. This paper, then, focuses on how the local people of Karimunjawa Island face that ecological threat. To answer the problem, we employed qualitative research. Data were collected by in-depth interviews with local tourism business people, local community members, and people from the local government office. In addition, data gathered from observation in Karimunjawa and document analysis. The results show that some ecological problems appear as a result of tourists' activities in Karimunjawa. For example, plastic waste from mineral water and food packaging along the beaches and small islands. Moreover, under the sea also has a problem, such as damaged coral reef. For local people, the awareness of this environmental damage is still low. In the following years, this could be a severe problem as tourism is a significant contribution to the economy of Karimunjawa. This research implies the importance of local awareness of environmental conservation because the community is the subject and the object of tourism development.