Tourism is one of the leading contributors to service industry in Malaysia and is gradually growing. The growth of this industry brings impact towards the environment, specifically the water quality of islands. This study views into the visitors and residents perception of the impacts of tourism towards the water quality of islands. A total number of 211 and 258 questionnaires were distributed to visitors Redang and Perhentian Island which are popular tourist destinations. Meanwhile, 188 residents from Redang and 183 from Perhentian were also distributed with the questionnaires. The results indicate that there is a high level of agreement that the water quality of both islands is affected by tourism for both visitors and residents. There were significant difference on the level of agreement between visitors and residents in Perhentian Island for items on sewage water and living things on the sea. Establishing carrying capacity and embedding environmental education in sustainable tourism management would help broaden the perception of visitors.