Mordaunt was returned as Member of Parliament for Brackley at a by-election on 2 January 1692 and was returned unopposed at the 1695 English general election. He was defeated in a contest at the 1698 English general election. In 1698, Mordaunt was appointed Conservator of the Forest of Dean until 1712.
Mordaunt was re-elected as Member of Parliament for Brackley in a by-election on January 2, 1692, and unopposed at the 1695 English general election. He lost an election in 1698 and became Conservator of the Forest of Dean until 1712.