After leaving college he resided for some time with Archbishop John Whitgift, then visited Italy, and took the degree of M.D.
On his return home he engaged in military service, and was with Sir John Norris and the Earl of Southampton in Ireland and the Netherlands.
In 1656 the college, on the proposition of Baldwin Hamey, voted the erection of a marble bust to his memory in the Harveian Museum; the statue was destroyed in the Great Fire of London of 1666, as was his monument in St Paul's.
He attended John Donne, Dean of St Paul's, and contributed liberally towards the erection of a monument to his memory.
The life of his father prefixed to the second volume of the 1641 edition of the Actes and Monuments, long attributed to his brother Samuel, has also been assigned, on weak grounds, to Simeon himself.