By the late 15th century Rockingham Castle had fallen into disrepair. Sir Edward Watson (founder of the Watson Family dynasty) acquired the lease of the castle from Henry VIII. Parts of the castle were subsequently replaced with a Tudor house with gardens. The former royal castle became a hunting lodge for the nobility. Watson's son Lewis Watson acquired the fee of the castle and lands from the crown. Watson was successively a knight, baronet and baron.
In the 1640s Rockingham was garrisoned by troops loyal to Charles I during the English Civil War. Several small skirmishes were fought with Parliamentary forces. In 1643 Rockingham was captured by Parliamentarian general Henry Grey, 1st Earl of Stamford. Its remaining walls were slighted in 1646.
In the latter 17th and 18th centuries, Rockingham returned to being a civil residence and family seat of the Marquesses of Rockingham. When Charles Watson-Wentworth, 2nd Marquess of Rockingham died in 1782. the estate among others passed to the son of his sister, William Fitzwilliam, 4th Earl Fitzwilliam. The castle underwent further restoration in the late 19th century.
Today the castle remains the private home of the Saunders Watson family.