According to the tradition that Venice would be the legitimate heir of ancient Rome, the Marcellos would be direct descendants of the Claudii Marcelli, which would have transplanted into the lagoon during the seventh century; here it would have contributed to the foundation of Rialto, giving tribunes.

Nevertheless, from the fourteenth century the Marcellos began to have an important role in Venetian public life, competing with the most prestigious families, the longhi (those who had been part of the nobility since a long time), in the division of offices.

[4] It was above all in the fifteenth century that the family became the protagonist of various political and military events: for example, Jacopo Antonio di Pietro (1397–1464 / 65), who was responsible for the liberation of Brescia and Verona occupied by the Visconti (with the notable enterprise of transporting of a fleet over the Adige by land); Nicolò di Giovanni (1397–1474) who, after a brilliant public career, was elected doge in 1473; Jacopo di Cristoforo (1413–1484), general da mar, who died during the conquest of Gallipoli; Pietro di Jacopo Antonio (1446–1530), who took part in the War of Ferrara (1482–1484), with which the Serenissima subdued Polesine.

[5] Two centuries later it was Lorenzo di Andrea (1603–1656) who distinguished himself in the fight against the Turks, directing the victorious expedition of the Dardanelles, in which, however, he lost his life.

After the fall of the Serenissima, the Marcellos were one of the few Venetian families to maintain a leading role in administrative life.