He was educated at Westminster School and Trinity College, Cambridge.
After leaving the university he entered public life as a servant of Sir Fulke Greville, later Lord Brooke, a client of Robert Devereux, second earl of Essex, afterwards becoming deputy-treasurer of the navy and then a commissioner of the navy, and being specially commended for his labours on behalf of naval administration. Coke was also acquainted with Essex from his university days. He was appointed a Master of Requests in 1622 and was knighted in 1624.
In 1624 he was elected Member of Parliament for Street Germans and was re-elected for the seat in 1625.
His actual appointment as secretary dates from September 1625. He was elected Member of Parliament for Cambridge University in 1626 and 1628.
Disliked by the leaders of the popular party, his speeches in the House of Commons did not improve the king"s position. King Charles ruled without a parliament from 1628 and he found Coke"s industry very useful to him.
Coke kept his post until 1639, when he was scapegoated for the humiliating Pacification of Berwick with the Scots.
Dismissed from office, he retired to his estate at Melbourne in Derbyshire, and then resided in London, dying at Tottenham on 8 September 1644. Coke in his earlier years had been a defender of absolute monarchy and greatly disliked the papacy. He was described by Clarendon as "a man of very dumb education and a narrower mind".
And again he says, "his cardinal perfection was industry and his most eminent infirmity covetousness."
The Coke family continued to own Melbourne Hall until George Lewis Coke, an ambiguous figure who died childless.
In the parliament of 1625 Coke acted as a secretary of state. In this and later parliaments he introduced the royal requests for money, and defended the foreign policy of Charles I and Buckingham, and afterwards the actions of the king.
In 1621 Coke was elected Member of Parliament for Warwick.