Urban forests provide many benefits for the city's resiliency to climate change by improving the degree of shading, evaporative cooling, rainwater interception, and storage and filtration functions. With the increasing population and unplanned urbanization, the Northern Forests, which play a major role in Istanbul, are being destroyed over time. In this study, forest area changes were determined by using object-based classification and landscape metrics. 2009 and 2019 dated Landsat TM and Landsat OLI&TIRs images were used to detect the changes, especially in forest areas in İstanbul. According to the classification results, forest areas decreased from 318.2 km² to 292.1 km², while urban areas increased from 87.2 km² to 104.6 km². Landscape metrics are calculated from the classification results for the forest areas. Landscape metrics were selected as aggregation index, edge density, the largest patch index, and patch density in this study. As a result, in the study area, due to an increase in patch density and edge density it is observed that fragmentation and heterogeneity increase, and also clustering, continuity of class types, and proportional distribution in the landscape decreased. The patch and edge density of urban areas, forest areas, roads, and bare areas has increased. Fragmentation has increased in forest and agricultural areas. Therefore, road and barren lands tend to cluster, while the clustering tendency has decreased in other classes.