De Fabris was born in Florence, Italy. He initially studied at the Academy of Fine Arts in Florence, then traveled to Rome, where he met the archeologist Antonio Nibby and to Venice where he met the historian and art-critic Pietro Selvatico. In 1857–1860, he helped design, alongside Michelangelo Maiorfi, the Palazzo della Borsa in Florence. He was professor at the Florentine Academy of Fine Arts and Architect to the Opera di Santa Croce.
