It is not known for how long a building has been present on the site, but the great hall is thought to have been built by 1470. The house was substantially upgraded in 1631-2 by Roger and Mary Mostyn, descendants of Ieuan Fychan, whose grandson had adopted the Mostyn surname. 
Since 1660 the hall has been the seat of the Mostyn Baronets, and since 1831, of the barons Mostyn. In the 1840s the 1st Baron Mostyn commissioned architect Ambrose Poynter to remodel the house, which was carried out mainly in 1846–47 in a Jacobean style inspired by the pre-existing building.
Porth Mawr is a Grade I listed former Tudor gatehouse block to the south west of the house which dates from 1570. Ornamental entrance gates leading to the house were designed in early 18th-century Baroque style by the Chester architect John Douglas and constructed by James Swindley in 1896. The gates, the associated piers and the bridge nearby are designated as a Grade II listed building.
The hall is still in the hands of the Mostyn family. Since 2014 it has been open to the public on a limited number of days in the year.
The GWR Hall Class locomotive no. 5985 was named after the hall.
- Mostyn Hall, Cadw, retrieved 21 August 2013
- "Mostyn Hall, Mostyn". British Listed buildings. Retrieved 25 August 2014.
- Hubbard, Edward (1986). The Buildings of Wales: Clwyd. London: Penguin. pp. 400–401. ISBN 0-14-071052-3.
- Entrance piers, gates and bridge to Mostyn Hall, Cadw, retrieved 21 August 2013
- "Mostyn Hall Opening to Public". Mostyn Estates. Retrieved 25 August 2014.