Giovanni was orphaned of his father at the age of 2 years, and his mother entrusted him to be educated under his uncle, canon in the Collegiate church in his birthplace.
Upon graduation, he spent a year in the circle of Anton Maria Salvini, an erudite scholar of Classic Greek literature and philosophy.
The next year he was appointed by the Grand Duke Gian Gastone to a position teaching ecclesiastical history at the University of Florence.
In 1736, Lami began his eighteen-volume Deliciae eruditorum, a "hodge-podge of antiquarian lore" published over a span of decades at Florence.
Among the topics, for example was a voyage (Hodeporicon) from Florence to his native Santa Croce dell'Arno, describing the chronology of events in the series of towns.
Lami also started and edited from 1740–1768 an erudite and scholarly journal, Novelle Litterarie, published in Florence and discussing subjects in all fields.
"[4][a] Lami was ultimately a defender of Catholicism, but one influenced by Jansenism, whose closest representatives in Italy were the Oratorians of Saint Philip Neri, but critical of the Jesuits and there official subserviance to the papacy.