In 1639, following the death of his father, Leti was sent by his mother to the Jesuit college at Cosenza, where he remained forcibly until 1644, when he accepted the invitation of his uncle Agostino to join him in Rome.
Orphaned at age 16, he was forced to return to his uncle, now a vicar in Orvieto and to adapt to the severe discipline of his tutor Don Agostino Cauli.
In 1654, his uncle Agostino, having failed to form his nephew in a suitable profession, finally gave Leti charge of his inheritance, leaving him free to travel.
[8] He wrote the first ever proper life of Elizabeth I of England, which includes many romantic embellishments about her youth and her mother, Anne Boleyn.
After the publication of a collection of anecdotes which offended Charles II, Il Teatro Britannico,[10] Leti fled England in 1683 for Amsterdam, where he became the city historiographer in 1685.
[10] Leti's biography of Pope Sixtus V has been translated into many languages, and contains an anecdote similar to the infamous "pound of flesh" from William Shakespeare's The Merchant of Venice.