[1][3] From 1521 to 1534[citation needed] he was employed as an assistant to Michelangelo Buonarroti at the Medici Chapel (Sacrestia Nuova) and in the Biblioteca Medicea Laurenziana at the Basilica of San Lorenzo in Florence.

This sculpture was probably intended for a wall fountain, possibly situated in a niche where the water would have flown from the open neck of the satyr's wineskin.

Restoration methods in that era entailed reworking sculptures in accordance with contemporary principles which often were at odds with the aesthetics of antiquity.

For instance, Montorsoli included a new right arm in the central figure of the Laocoön group, upraised in a gesture of defiance, adding much to the fame of the sculpture and himself.

On polygonal basin's rim are the statues of four river gods (Tiber, Nile, Camaro and Ebro) with Latin inscriptions by the scientist-humanist Francesco Maurolico who, probably, was also the creator of most of the Neoplatonic-alchemical program for the fountain.

In the middle of the fountain Cellini wanted to erect a "pedestal, projecting somewhat above the margin of the basin, and upon this a nude male figure" which was to represent the King himself as Mars.

This work was especially influential in Florence, which had an affection of colossal statuary, and it likely influenced designs for Ammanati's Neptune Fountain in the Piazza della Signoria.

Montorsoli left some of his works in Genoa in the church of San Matteo, commissioned by Andrea Doria, for his tomb and some sculptures.

Montorsoli was instrumental in the foundation in 1562–1563 of the Accademia delle Arti del Disegno, which was the academy of art and of artists in Florence until 1784, and which at first met in the Servite church of the Santissima Annunziata where Montorsoli had worked on the decorations of the Cappella dei Pittori, in which the order had given permission for artists to be buried.

The Accademia was formed under the patronage of Cosimo I de' Medici, Grand Duke of Tuscany, and with the support of Giorgio Vasari.