It is situated between Langeoog to its west, and Wangerooge to its east. The island also forms a municipality of the district of Wittmund, in Lower Saxony. The only village on the island is also called Spiekeroog.
Spiekeroog covers an area of 18.25 km², the shortest distance to the mainland is 5.7 km. The island is - with the exception of fire and rescue vehicles - free of cars. A daily ferry service with the harbor of Neuharlingersiel connects the island with the German mainland.
The origination of the name "Spiekeroog" is controversial. Today, most of the people tend to believe that it is a translation of "storage island".