The islands extend for some 90 kilometres (56 mi) from west to east between the mouths of the Ems and Jade / Weser rivers and lie about 3.5 to 10 km offshore.

Between the islands and the mainland are extensive mudflats, known locally as Watten, which form part of the Wadden Sea.

The islands, the surrounding mudflats and the territorial waters (The Küstenmeer vor den ostfriesischen Inseln nature reserve) form a close ecological relationship.

The island group makes up about 5% of the Lower Saxon Wadden Sea National Park.

In 2003 the German Coastal Defence (NLWK) announced that the sandbank Kachelotplate can now be called an island too, because it is no longer regularly flooded by high tide.

German students memorize the names of the seven inhabited islands by using a mnemonic device: