Istanbul, being one of the oldest and crowded cities in the world bridging the Asia and Europe continents, is ranked as the 15th populated mega city among the 75 largest metropolitans in the world as a result of the rapid population growth since the year of 1950. The stated growth caused a significant need for housing, therefore new settlements have been built in and around the city threating water resources, protected areas, and sensitive lands such as agricultural areas, forests, wetlands in the city. As a result of these adverse developments, the Bosphorus zone, which has a historical and geographical importance for Istanbul, was declared as a protected zone for stopping the threat of unplanned urbanization along the Bosphorus. The Bosphorus area were divided in to two protection zones as Back View and Front View Zones by the laws in terms of the stated protection plan. The main goal of this study is to examine the changes in settlement areas in the protected zones of Bosphorus specifically in Sariyer District. In this context, Landsat imageries dated 2005 and 2017 were used to determine the urban sprawl during 12 years in the protection zone of Bosphorus. The results of the study introduced 10% decrease in the forest and green lands from 2005 to 2017 while 8% and 11% increase in settlements and the other land use classes respectively. In order to perform more detailed analyses of this change, a detailed study was performed for Front and Back View Zones of Bosphorus in Sariyer district using 2005 and 2017 dated IKONOS satellite images. The map of Sariyer district produced in 1960 was considered as the reference data source as well as image for detecting the changes in the study area during 57 years in two periods. The results of the study outlined that the settlements in the study area increased 173% and 142% for two periods from 1960 to 2005 and from 2005 to 2017 respectively. The increase in settlement areas caused a decrease in forests and green lands in the study area. In particular, the study introduced the illegal settlement area increase in the protection zones of the Bosphorus based on the Bosphorus Law No. 2960 in Sariyer District.