Ferrini possibly began his apprenticeship at Cristofori's workshop circa 1710, when he was twelve, and subsequently worked as the principal assistant. Giovanni continued making various instruments invented by his teacher, including spinettone da orchestra (a large bent-side spinet designed for use with an opera orchestra) and fortepianos with hammered action. He also made psalteries (zithers) and gut-strung harpsichords. Between 1731 and 1756, Giovanni Ferrini worked for the Tuscan court. He registered in the Università di Por San Piero e dei Fabbricanti guild in 1736. One of Ferrini's last known works was a restoration of Girolamo Zenti's 1658 harpsichord he completed in 1755 (currently preserved at Metropolitan Museum Of Art in New York). After Giovanni Ferrini passed away, his two sons, Giuseppe Ferrini (1733—1783) and Filippo Ferrini (1734—1795), continued the family oeuvre.