Henslowe's modern reputation rests on the survival of his diary, a primary source for information about the theatrical world of Renaissance London.
Henslowe is recorded working as assistant to Henry Woodward, reputed to be the bailiff for Anthony Browne, 1st Viscount Montagu, owner of Cowdray House and Battle Abbey in Sussex.
Henslowe developed extensive business interests, including dyeing, starch-making, pawn-broking, money lending and trading in goat skins.
From 1591, Henslowe partnered with the Admiral's Men after that company split with The Theatre's James Burbage over the division of receipts.
John Taylor, the "Water Poet", petitioned the King on behalf of the Watermen's Company, because of the expected loss of business transporting theatre patrons across the Thames.
Henslowe and Alleyn also operated the Paris Garden, a venue for baitings; early in James's reign, they purchased the office of Keeper of the Royal Game, namely bulls, bears and mastiffs.
The introduction to Ben Jonson's Bartholomew Fair, performed at the Hope in 1614, complains that the theatre is "as dirty as Smithfield, and as stinking every whit."
It is a collection of memoranda and notes that record payments to writers, box office takings, and lists of money lent.
The diary is written on the reverse of pages of a book of accounts of his brother-in-law Ralf Hogge's ironworks, kept by his brother John Henslowe for the period 1576–1581.
Entries continue, with varying degrees of thoroughness (authors' names were not included before 1597), until 1609; in the years before his death, Henslowe appears to have run his theatrical interests from a greater distance.
It also shows Henslowe to have been a careful man of business, obtaining security in the form of rights to his authors' works, and holding their manuscripts, while tying them to him with loans and advances.
In 1598 Henslowe made an inventory of his company's stage props; 'along with numerous weapons and crowns, there was a boar's head, a wooden leg, a golden fleece and the cauldron in which Marlowe's Jew of Malta is boiled to death.