At the age of 20 he was named commander of the Venetian fleet, performing distinguished service as a soldier; he waged successful campaigns against the Dalmatian pirates.

[3] In 976, the sitting doge, Pietro IV Candiano, was killed in a revolution that protested his attempts to create a monarchy.

[4] As doge, Orseolo demonstrated a good deal of talent in restoring order to an unsettled Venice and showed remarkable generosity in the treatment of his predecessor's widow.

Out of his own resources he began the reconstruction of the ducal chapel, now St. Mark's Basilica, and the Doge's Palace, which had been destroyed during the revolution, along with a great part of the city.

Orseolo is venerated as a saint by the Roman Catholic Church, his cultus having been confirmed by his equivalent canonization in 1731 by Pope Clement XII, who set his feast day for 14 January.