Herbert was born at Werrington, Devon, the 7th son of Thomas Herbert, 8th Earl of Pembroke of Wilton House, and his first wife Margaret Sawyer of Highclere Castle, daughter of Sir Robert Sawyer MP of Highclere, Hampshire.
He was educated probably at Eton College in 1725 and matriculated at Christ Church, Oxford on 2 December 1726, aged 20.
[2] Herbert was returned as Member of Parliament for Newport in a by-election on 22 January 1740 on the Morice interest.
He was returned unopposed at Newport in 1747 and in a contest in 1754[3] In 1756 Herbert vacated his seat at Newport and was returned in a by-election on 17 April 1757 as MP for Wilton on the interest of his nephew Henry Herbert, 10th Earl of Pembroke.
However he lost his place as treasurer when George III came to the throne and was frustrated at not being offered any other post.