Aga Town is situated in the east of Niigata Prefecture. You can reach the town center in about 35 minutes via the Banetsu Expressway, or about 60 minutes on National Route 49 driving east from Niigata City, the prefectural capital. The east side of the town borders on Fukushima Prefecture.
The Agano River and its tributary, the Tokonami River, flow in the center of Aga Town which is a mountainous region developed on the terraced fields along these rivers. The town center is relatively flat, but is surrounded by steep mountains. The massif of Mt. Iide extends widely in the north and the Echigo Mountains run in the northwest from north to south.
The town area is 952.89 km2, occupying about 7.6% of Niigata Prefecture.