In August or September 1622, his feuds with some prominent Mantuans led him to move to Venice, which for the first few decades of the seventeenth century had persisted in sponsoring Mannerist styles (epitomized by Palma the Younger and the successors of Tintoretto and Veronese). Into this mix, in the 1620s–30s, three "foreigners"—Fetti and his younger contemporaries Bernardo Strozzi and Jan Lys—breathed the first influences of Roman Baroque style. They adapted some of the rich coloration of Venice but adapted it to Caravaggio-influenced realism and monumentality.
In Venice where he remained despite pleas from the Duke to return to Mantua, Fetti changed his style, and his formalised painting style became more painterly and colourful. In addition, he devoted attention to smaller cabinet pieces that adapt genre imaging to religious stories. His group of paintings entitled Parables, which represent New Testament scenes, are at the Dresden Gemäldegalerie. He influenced Leonaert Bramer.
His style appears to be influenced by Rubens. He would likely have continued to find excellent patronage in Venice had he not died there in 1623 or 1624. Jan Lys, eight years younger, but who had arrived in Venice nearly contemporaneously, died during the plague of 1629-30. Subsequently, Fetti's style would influence the Venetians Pietro della Vecchia and Sebastiano Mazzone.