He was the third son of John Beaufort, 1st Earl of Somerset. As a young man he became a commander in the English army in France. After his re-capture of Harfleur he was named a Knight of the Garter in 1436. After subsequent success he was created Earl of Dorset (1442) and the next year Marquess of Dorset. The year after that (1444) he succeeded his brother John as 4th Earl of Somerset in 1444.
During the five year truce from 1444 to 1449, Somerset was Lieutenant of France. In 1448 he was created Duke of Somerset. (He is usually called 2nd duke since his brother John had also been duke, though strictly speaking of a separate creation.)
Somerset found military success elusive after hostilities begain again in 1149. By the summer of 1450 the bulk of the English possessions in northern France were in French hands. This loss lead to the fall of the king's chief minister, William de la Pole, 1st Duke of Suffolk. Somerset returned to England, where he took Suffolk's place as the king's counselor. He was a favorite of the Queen, Margaret of Anjou. In fact some claimed that Edward of Westminster, the young Prince of Wales was his son, and not the king's.
The focus of the war with the French now turned to Gascony, in the south of France. Here the English were no more successful, losing all by 1453. Soon afterwards the king went insane, Somerset's rival Richard, Duke of York was named Lord Protector, and Somerset was imprisoned in the Tower of London. He life was probably saved only by the king's recovery. Henry VI had Somerset released and returned to his position at court.
The Duke of York was determined to depose Somerset by one means or another, and thus in 1455 he confronted Somerset and the king with an armed force. Somerset was killed in the resulting engagement, known as the first Battle of St Albans. It was the beginning of the Wars of the Roses, which would go on to claim many of Somerset's sons and relatives.
He was succeeded as duke by his son Henry.
Somerset married Eleanor Beauchamp, daughter of Richard de Beauchamp, 13th Earl of Warwick sometime between 1431 and 1435 in a unlicensed marriage. This was later pardoned on 7 March 1438, and they had the following children:
| Preceded by: New Creation | Duke of Somerset | Followed by: Henry Beaufort |
| Preceded by: John Beaufort | Earl of Somerset | Followed by: Henry Beaufort |