South Hook Fort was built between 1859 and 1860 as one of the Palmerston Forts. The main building is a two storey barrack building. To the front of the Fort lies a number of gun emplacements covering the main harbour entrance.
The initial armament was twenty guns, fifteen 7-inch RML and five 9-inch RML.
The Barrack block and flanks of the gun battery were protected by a dry ditch that stretched to the sea shore.
South Hook Fort became an important component of the main coastal defence line which included Chapel Bay Fort, the submarine minefield, and Stack Rock Fort. The Submarine Mining Depot was located at Pennar Point near Pembroke.