The demilitarized zone (DMZ) in Korea, a 4-km-wide military-free zone at the border between South Korea and North Korea, has been well preserved for half a century and has a high ecological value. However, temporal and spatial data are lacking owing to poor accessibility. In this study, we detected object-based land cover changes using Landsat-5 TM, Landsat-7 ETM, and Landsat-8 OIS, and identified changes around the DMZ through landscape structure analysis. The land cover was classified into six categories, namely, settlements, cropland, wetlands, forest land, semiforest land, and bare land by object-based classification. The landscape structure was analyzed using five landscape metrics [i.e., number of patches (NumP), mean patch size (MPS), total edge (TE), edge density (ED), and area-weighted mean shape index (AWMSI)]. Results showed that, from 2000 to 2009, the forest land and bare land areas decreased, while the semiforest land area increased. In 2009–2019, the bare land area increased, while the forest land area decreased. Consequently, the restoration of wildfire-damaged areas decreased the fragmentation of Goseong-gun in 2000–2009 and wildfire caused more forest damage in 2009–2019.