They were vassals of the De Morevilles, a powerful Anglo - Norman family with vast estates around Largs and Irvine. The earliest record of them is in the burgh of Irvine in 1205, when Robertus de Boyd witnessed a contract between the Lord of Eglinton and the burgh of Irvine, Robert de Boyte is listed in the Ragman Roll of 1296, rendering homage to Edward I of England. the name soon became fairly common, especially in Ayrshire.

Duncan Boyd was executed as a partisan of Robert Bruce by the English in 1306, Sir Robert Boyd was a staunch supporter of Bruce and was one of the commanders at the Battle of Bannockburn in 1314. His gallantry on the field of battle was rewarded by lands which were confiscated from the Balliols, including Kilmarnock, Bondington and other substantial holdings in Ayrshire.

Robert Boyd, created Lord Boyd in 1454, became regent for the infant King James III after an accident with a siege gun killed James II in 1460. He arranged the marriage of the king to a Norwegian princess. This liaison resulted in the return of the Orkneys and Shetlands to the Scottish Crown, his younger brother was appointed military tutor to the young king. The influence of the Boyd brothers on their young charge was considerable. Lord Boyd was appointed Great Chamberlain, and his son, Thomas, was married to Princess Mary, the king's sister, with the title of "Earl of Arran."

The Boyds were viewed with suspicion and when James III grew older those that opposed them began to conspire against them, and eventually persuaded the young king that the ambition of this family was a threat to the throne itself.

In 1469, Lord Boyd, his son, the Earl of Arran, and his brother, Alexander Boyd, were summoned to appear before the king and Parliament to answer charges brought against them. Lord Boyd, realizing that appearance in Edinburgh would result in his death, made his escape to England. Sir Alexander, who was already a sick man, was brought before Parliament, and despite making a spirited defense he was executed for treason.

The Earl of Arran had been abroad on state business, and on learning of these events his exile, and was well received at royal courts throughout Europe. The king, who had now abandoned entirely his former mentors, summoned his sister back to Scotland, inducing her to come on the presence that he might yet forgive her husband. The deluded princess returned, and was promptly detained by her brother who procured an annulment of her marriage, she was then compelled to marry the elderly Lord Hamilton, whose family then supplanted the Boyds in nearness to the throne. The Hamiltons gained not only a royal wife from the Boyds but also the earldom of Arran.

The family were restored to royal favour when Robert, a descendent of the younger son of the first Lord Boyd, received confirmation from Mary, Queen of Scots, of all the estates, honours and dignities of the family, with the title of 'Lord Boyd'. After the queen's escape from Loch Leven Castle, Lord Boyd was one of the first to join her at Hamilton, and fought at the Battle of Langside. He thereafter made many visits to her during her captivity in England. He died in 1590. The family adhered to the cause of the king during the civil war, and they received their reward after the Restoration when William, Lord Boyd, was created Earl of Kilmarnock in 1661.

The third Earl opposed the Stuart claim during the rising of 1715 and commanded a regiment of Ayrshire volunteers. His son, the fourth Earl, did not share his father's sympathies and fought for Prince Charles Edward Stuart, the 'Young Pretender', who appointed him a member of the Privy Council with the rank of general. He commanded a troop of cavalry at the Battle of Culloden where he was captured. He was conveyed to the Tower of London and was beheaded on Tower Hill on 18 August 1746. All the Boyd titles were declared forfeit, but his eldest son succeeded through his mother to the earldom of Erroll in 1758, and assumed the name of Hay.

The eighteenth Earl of Erroll was created Baron Kilmarnock in the peerage of the United Kingdom in 1831. The twenty-second Earl of Erroll died in Kenya in 1941 leaving a daughter who, although entitled to succeed to the Scottish earldom of Erroll and the chiefship of Clan Hay, was excluded from the barony of Kilmarnock which, as a United Kingdom title, could only pass to males. Consequently, the brother of the twenty-second Earl changed his own name back to Boyd and became known as Lord Kilmarnock and Chief of Clan Boyd.