Alvise Cadamosto was born at the Ca' da Mosto, a palace on the Grand Canal of Venice from which his name derives.

His father was Giovanni da Mosto, a Venetian civil servant and merchant, and his mother Elizabeth Querini, from a leading patrician family of Venice.

Alvise is the eldest of three sons, having younger brothers Petro and Antonio.

At a remarkably young age, Cadamosto had cast out as a merchant adventurer, sailing with Venetian galleys in the Mediterranean.

From 1442 to 1448, Alvise has undertaken various trips on Venetian galleys to the Barbary Coast and Crete, as a commercial agent of his cousin, Andrea Barbarigo.

He had been appointed noble officer of the marine corps of crossbowmen on a galley to Alexandria in 1451.

The next year, he had served the same position on a Venetian galley to Flanders, returning to find his family disgraced and dispossessed.

His father, caught in a bribery scandal, had been banished from Venice, and taken refuge in the Duchy of Modena.

His Querini relatives had taken the opportunity to seize possession of his family's property.

This setback had marred the future prospects of Cadamosto's career in Venice, and probably encouraged his spirit of adventure, hoping to restore his family name and fortune by great feats of his own.

At the age of twenty-two, Alvise and his brother Antonio had embarked in August, 1454, on a Venetian merchant galley, captained by Marco Zen, destined for Flanders.

On the outward journey, the galley had been detained by bad weather near Cape St. Vincent, Portugal.

While waiting for the weather to improve, the Portuguese Prince Henry the Navigator, who has his seat nearby at Sagres, had dispatched a couple of his commercial agents, led by his secretary Antão Gonçalves and the local Venetian consul Patrizio di Conti, to interest the stranded Venetian merchants into opening trade contracts for sugar and other goods from the prince's Madeira island.

Informed by the visitors of Henry's recent discoveries in Africa, Cadamosto immediately applies to Prince Henry at his residence at Raposeira to undertake an expedition on his behalf.

Henry hires him on the spot.

Setting out on March 22, 1455, on a forty-three-ton caravel supplied by Prince Henry, with Vicente Dias as ship master, Cadamosto had proceeded to Porto Santo and Madeira, and thereafter has woven his way through the Canary Islands, making stops in La Gomera, El Hierro and La Palma before reaching the African coast around Cape Blanc.