He fought in the Parliamentary army in the English Civil War. Bennet was the eldest son of Richard Bennet, of Lawhitton, Cornwall. He matriculated at Exeter College, Oxford on 13 December 1622, aged 17 and was awarded Bachelor on 25 October 1624.
He was a student of the Middle Temple in 1622.
Bennet was a Parliamentary colonel, and governor of Saint Michael"s Mount and Saint Mawes Castle in the Civil War. He was elected Member of Parliament for Launceston in 1654 for the First Protectorate Parliament.
Bennet died at the age of 79 and was buried at Lawhitton on 7 July 1683.