In 1710 he became a pupil of Gregorio Lazzarini, a successful Painter with an eclectic style. He was, though, at least equally strongly influenced by his study of the works of other contemporary artists such as Sebastiano Ricci and Giovanni Battista Piazzetta and those of his Venetian predecessors, especially Tintoretto and Veronese. A biography of his Teacher, published in 1732, says that Tiepolo "departed from [Lazzarini's] studied manner of painting, and, all spirit and fire, embraced a quick and resolute style". His earliest known works are depictions of the apostles, painted in spandrels as part of the decoration of the church of the Ospedoletto in Venice in 1715–6. At about the same time he became Painter to the Doge, Giovanni II Cornaro, and oversaw the hanging of pictures at his palace, as well as painting many works himself, of which only two portraits have been identified. He painted his first fresco in 1716, on the ceiling of a church at Biadene, near Treviso. He probably left Lazzarini's studio in 1717, the year he was received into the Fraglia or guild of Painters.