He was educated at Brasenose College, Oxford, which he left without a degree, and the Middle Temple, from where he was called to the bar.
In 1559 he was one of the commissioners to visit the dioceses of Oxford, Lincoln, Peterborough, Coventry, and Lichfield, and in 1568 he became "double reader in Lent" to the Middle Temple.
As Recorder of London he was famous for rigorously and successfully enforcing the laws against vagrants, mass-priests, and other papists.
In 1576 Fleetwood was committed to the Fleet prison for a short time for breaking into the Portuguese ambassador's chapel under colour of the law against popish recusants.
In the same year he drafted a scheme for housing the poor and preventing the plague in London by maintaining open spaces.
He had formerly lived at Bacon House, Foster Lane, and at his death owned an estate at Great Missenden, Buckinghamshire, where he was buried.
[3] Also left was Itinerarium ad Windsor, an unpublished work relating to the succession to Elizabeth I of England.
In this work he describes a (fictional) dialogue, in which he takes part with the Earl of Leicester and Baron Buckhurst.