The Old Korean Legation building was designed and constructed by American architect Thomas M. Plowman in 1877. The three-story building with a basement was built on a site of 381.10㎡, with a building area of 152.43㎡, and has the total floor area of 584.54㎡.
The Old Korean Legation building has been restored to its original conditions based on documents and photographs from the late nineteenth and early twentieth centuries that were recently discovered in Korea and overseas. The first and second floors, which had remained relatively unchanged, have been restored to reflect the appearance of the Old Korean Legation at the time of its operation. The third floor, which had undergone considerable renovations over time, has been remodeled to provide an exhibition space. As part of the restoration and remodeling processes, a small traditional Korean garden of about 961ft² was added.