Ilioupoli is 6 km (4 mi) southeast of Athens city centre. The municipality has an area of 12.724 km2. It lies at the western foot of the forested Hymettus mountain, which covers the eastern half of the municipality. Its built-up area is continuous with those of neighbouring suburbs Ymittos, Agios Dimitrios, Alimos and Argyroupoli. The main thoroughfares are Vouliagmenis Avenue, which connects Ilioupoli with central Athens, and Venizelou Avenue, which connects with Motorway 64. Ilioupoli station is served by Line 2 of the Athens Metro. Ilioupoli is also linked by bus to downtown Athens (OASA 237 line), to Glyfada (OASA 140 line) and Piraeus (OASA 218 line).
Ilioupoli is subdivided into 11 quarters: Agia Marina, Agia Mavra, Agia Paraskevi, Agios Konstantinos-Kanaria, Ano Ilioupoli, Astynomika-Panorama, Kato Ilioupoli, Kentro, Nisaki, Typografika and Chalikaki. Ilioupoli has an uncommon street plan, characterised by 5 sets of concentric circular or oval streets.