Gangdong-gu is located in the southeastern part of Seoul. It is adjoined to Guri-si, Gyeonggi-do in the north via Hangang(River), and to Gwangjin-gu in the west via Cheonhodaegyo. It is also next to Hanam-si, Gyeonggi-do in the east, and to Songpa-gu in the south via Gangdongdaero.

The area of Gangdong-gu is 4.1% of the total area of Seoul, 24.56㎢.
It is divided into 19 administrative districts(Dong).

• Residential area 12.94㎢ (52.7%)
• Green area 10.83㎢ (44.1%)
• Commercial area 0.71㎢ ( 2.9%)