The island has an area of 489 square kilometres, making it the tenth largest island in Norway. The island is connected to the neighboring island of Hinnøya using the Andøy Bridge. The Andfjorden lies to the east of the island, the Risøysundet strait lies to the south and east side of the island, and the Gavlfjorden lies to the southwest side. The Norwegian Sea lies to the west and north.
The numerous bog areas on Andøya are used for the extensive production of peat. Andøya is also well known for its cloudberries. Besides the flat and largely continuous bog areas, Andøya also consists of steep mountain ranges reaching up to 700 metres high. The sharp peak of Kvasstinden is the highest point on the island at 705 metres. The Andøya Rocket Range which was founded in 1962 is also located on the island.