Kingswear Castle is located low on the rocks on the eastern is of the habour entrance and consists of a small rectangular block and a later, smaller round tower. Kingswear was adapted by Henry VIII to house canons. Over time this smaller castle became less important. Dartmounth Castle is the larger of the two and was orginally build in the late fourteenth century. It was improved upon in around 1481 to house guns that could overlook the entrance to Dartmouth harbour. It consists of a large square tower with a lookout turret on the top. Beside the square tower is a round tower from which a chain was attached to the round tower at Kingswear on the other side of the harbour entrance. This chain was raised during the night to guard against enemy ships entering unseen.
The castles were held by the the Royalist supporters of King Charles I during the English Civil War but were captured by Sir Thomas Fairfax in 1646.