Pride is stated to have been brought up by the parish of St Bride's, London but is thought to have been born in Somerset. Subsequently he was a drayman and a brewer. At the beginning of the Civil War he served as a captain under Essex, and was gradually promoted to the rank of colonel. He distinguished himself at the Battle of Preston, and with his regiment took part in the military occupation of London in December 1648, which was the first step towards bringing King Charles I to trial.
The next step was the expulsion of the Presbyterian and Royalist elements in the House of Commons, who were thought to be prepared to reach a settlement with Charles. This, resolved by the army council and ordered by the lord general, Fairfax, was carried out by Colonel Pride's regiment. Taking his stand at the entrance of the House of Commons with a written list in his hand, he caused the arrest or exclusion of the members, who were pointed out to him. After about a hundred members had been thus dealt with, the mutilated House of Commons, now reduced to about eighty in number, proceeded to bring the king to trial. This marked the end of the Long Parliament and the beginning of the Rump Parliament.
Pride was one of the judges of the king and signed his death-warrant, appending to his signature a seal showing a coat of arms.
When the Commonwealth was established, he abandoned his involvement in politics, except in opposing the proposal to confer the kingly dignity on Cromwell. He was knighted by the Protector in 1656, and was also appointed to the second house added to Parliament as a result of the Humble Petition and Advice.
Pride died at Nonsuch Palace, an estate which he had bought in Surrey. After the Restoration of 1660 his body was ordered dug up and suspended on the gallows at Tyburn along with those of Cromwell, Henry Ireton and John Bradshaw, though it is said that the sentence was not carried out (probably because his corpse was too decayed).