The patronage of his kinsman, the Duke of Newcastle, obtained for him an appointment as secretary to British diplomats in France, and a Parliamentary seat at Hastings, from 1728 to 1741.
[2] His second cousin once removed, the Duke of Newcastle, brought him into Parliament at Hastings in 1728, where Thomas Townshend had left a vacancy by opting to sit for Cambridge University.
These duties did not keep him from a diligent attendance in Parliament, where he rarely missed recorded votes.
He and the incumbent, John Morley Trevor, successfully stood off a repeated challenge by Nathaniel Sergison.
Not long after, the younger Pelham began to suffer from tuberculosis, and died of that disease on 1 August 1743, during his father's lifetime.