Ruperra Castle was built by Sir Thomas Morgan, one of the most powerful men in Wales at that time, as steward to the Earl of Pembroke. As Surveyor of the Wood to King James I, he had been knighted in 1623. The revenue from these occupations, together with a favourable marriage, enabled him to complete the building of his house at Ruperra in 1626 probably on the site of an earlier mediaeval house. The architect is unknown.

Ruperra was deemed 'fit for a king' in 1645 when King Charles I stayed from 26th -29th July, longer than at Tredegar House or Llancaiach Fawr - gathering support in South Wales after his defeat at the Battle of Naseby. Sir Thomas' grandson, was host on this occasion and the royal coat of arms was added to the decoration on the South Porch. The present public footpath from the Rudry approach to the Castle is still known as the 'King's Drive.'