The two-storey building at Winkleigh Airfield, Devon, along with 9.5 acres of land and disused outbuildings, will go under the hammer next month.
The airbase was built in 1940 on remote moorland to defend Britain's western approaches from the Luftwaffe.
It was so strategically important that its existence was officially denied.
The watch tower and land is being sold on behalf of the official receiver at Clive Emson Auctioneers on 22 September at St Mellion in Cornwall and has a freehold guide price of between £35,000 and £50,000.
The tower is listed by English Heritage as a Scheduled Monument.
A former aircraft watch tower at one of the RAF's most secret World War Two bases has been put up for sale.