Mildmay was the second son of William Mildmay, of Moulsham, Essex. He was admitted at Emmanuel College, Cambridge in 1614 and admitted at the Inner Temple in 1616. He was adopted as heir to his uncle Sir Gawen Hervey in 1622 and adopted the additional surname of Hervey.
In the Civil War, he commanded a Parliamentary regiment and only escaped capture by swimming the moat of his manor house.
In 1654, he was elected Member of Parliament for Essex in the First Protectorate Parliament. He was re-elected MP for Essex in the Second Protectorate Parliament. After the Restoration he successfully pleaded to return to his post in the Jewel House.
Mildmay was of Marks, Romford, Essex. He died at the age of 80 and was buried at Romford on 8 August 1676. He had married Dorothy Gerard, sister of Sir Gilbert Gerard, 1st Baronet of Harrow on the Hill.
- HMC 7th Report (St John Mildmay) (London, 1879), p. 594.
- "Mildmay, Carew (MLDY614C)". A Cambridge Alumni Database. University of Cambridge.
- Willis, Browne (1750). Notitia Parliamentaria, Part II: A Series or Lists of the Representatives in the several Parliaments held from the Reformation 1541, to the Restoration 1660 ... London. pp. 229–239.
- "MILDMAY, Carew Hervey (1691-1784), of Marks, Essex, and Hazlegrove, Som". History of Parliament. Retrieved 13 June 2013.
|Parliament of England|
| Member of Parliament for Essex
With: Sir William Masham Bt 1654
Richard Cutts 1654
Herbert Pelham 1654
Sir Henry Mildmay 1654–1656
Sir Thomas Honeywood 1654–1656
Sir Thomas Bowes 1654–1656
Thomas Coke (of Pebmarsh) 1654
Sir Richard Everard, 1st Baronet of Much Waltham 1654–1656
Dionysius Wakering 1654–1656
Edward Turnor 1654–1656
Oliver Raymond 1654–1656
Sir Harbottle Grimston 1656
Robert Barrington 1656
Dudley Temple 1656
Hezekiah Haynes 1656
John Archer 1656