He served twice as Member of Parliament for Devon, on both occasions together with his brother Sir William Cary, in 1363/4 and 1368/9, and in November 1386 he was appointed Chief Baron of the Exchequer.
Attainder
He was a strong adherent to King Richard II and was attainted in 1388 by the Merciless Parliament, at which many members of Richard II's Court were convicted of treason. He was initially sentenced to death for his part in the "Nottingham judgements", but this was commuted to banishment to Ireland with a pension of £20. His landholdings and goods were thereupon forfeited to the Crown. Many of his forfeited lands in Somerset, including Hardington Mandeville, a moiety of Chilton Cantelo, and premises in Trent were sold by the crown in July 1389 for 600 marks, jointly to Sir John Wadham of Edge, Branscombe in Devon and Merryfield, Ilton, Somerset, Justice of the Common Pleas and MP for Exeter in 1399 and for Devon in 1401, together with Sir William Hankford of Annery in the parish of Monkleigh in Devon, Chief Justice of the King's Bench. His son and heir Sir Robert Cary married as his second wife Jane Hankford, daughter of Sir William Hankford and, according to Sir John Vivian, the widow of Sir John Wadham, although the will of John Wadham does not appear to support Vivian's contention. The attainder was reversed in 1398.
Landholdings
Sir John Cary appears to have had his principal home at Cary, thought by some to be Castle Cary in Somerset but in fact at St Giles on the Heath in Devon, where the ancestral estate of Carey Barton continues in other hands. He purchased the manor of Clovelly, on the north coast of Devon, where a junior branch of his descendants was seated until 1739 when it was sold to Zachary Hamlyn . His son and heir Robert Cary is generally stated to have been the first of the family seated at Cockington, on the south coast of Devon in Torbay. He also held a moiety of the manor of Great Torrington, Devon, possibly inherited from his heiress mother's family, de Bryan, which had inherited a one-fifth moiety of the feudal barony of Great Torrington from the Sully family.
Marriage and children
In 1376 he married Margaret Holleway, daughter and heiress of Robert Holleway of Holleway in the parish of North Lew in Devon. The arms of "Holway of Holway" are Gules, a fesse between three crescents argent and appear quartered by Cary on the monument in Clovelly Church of Robert Cary. Their children included three sons:
Sir Robert Cary of Cockington, Devon, twelve times MP for Devon.
