Pendennis Castle was built by Henry VIII between 1540-2, and lies opposite St Mawes Castle. The original Henrician fortifications, similar to St Mawes in design, is now absorbed into a much large fort with a bastion trace.
During the Victorian Period Pendennis Castle was used not only for barrack accommodation but also as the centre for coastal defence batteries working in conjunction with the fixed defences at St Mawes Castle. In 1855 the ramparts of the Castle mounted seven 56-pdr shell guns and fiver 32-pdr SB guns. These were replaced by new batteries with the principal being:
- 12-pdr Battery No.2 (Carrick) Bastion with two guns and underground works
- 12-pdr Battery No. 3 (West) Bastion with two guns and underground works
- One Gun Battery, a single emplacement for a 6-inch BL gun on a HP mount. Built in 1894, Bastion No.4 with adjacent underground works.
- Half Moon Battery built in front of Bastion Number 4 and Pigs Pound Bastion which was a later 6-inch BL Battery
- Pendennis Practice Battery built in 1898 on Pigs Pound Bastion. Armed with four 68-pdr guns, and in 1900 a 5-inch gun was added on a Vavasseur Mount.
In addition a new barrack block was built in 1902 to accommodate the 105th Regiment of the Royal Garrison Artillery. A Port War Signal Station (PWSS) was also constructed on the top of the old keep.
Crab Quay Battery was built outside the main fort and was armed with two 12-pdr Q.F. guns.