Gyrn Castle belonged in the early 17th century to the Mostyns of Cilcain. In 1749 ownership passed to the Reverend Samuel Edwards of Pentre Hall by his marriage to Charlotte Mostyn. The castle was sold in 1750, and passed by inheritance through three owners until its sale in 1817 to John Douglas, a cotton manufacturer. Douglas remodelled the house in 1817–24, probably by adding a third storey, expanding the floorplan with the addition of the projecting dining room at the north end and a picture gallery and tower at the south end. The Douglas family sold Gyrn in 1853 to Edward Bates of Hampshire, a ship owner and politician. He did little to alter the house, but did add numerous outbuildings. The mansion was listed on 17 February 1983 “as a C19 country house notable for its castellated style typical of the C19 Picturesque movement, the result of remodelling an earlier house on the site”.
Gyrn Castle remains in the ownership of the Bates family. The 2,000-acre (810-hectare) grounds now include two fishing lakes and facilities for shooting game. The house itself is hired out for wedding receptions and filming.