Born into a wealthy Genoese family in Spain, he studied classical literature in Arezzo and Rome.
Later holding a chair at the Collegium Gregorianum he published a collection of Latin orations and conducted influential research on the text of the Roman author Cicero.
Girolamo Lagomarsini was born on 30 September 1698 at El Puerto de Santa María (Spain), of a wealthy Genoese family.
In 1732 he was appointed to the chair of rhetoric at Florence, and in 1751 to that of Greek in the Collegium Gregorianum at Rome, which position he occupied until his death on 18 May 1773.
Barthold Georg Niebuhr was the first to make use of Lagomarsini's vast collection of various readings preserved in the Roman College.