His father was a tailor named Niccolò di Dello.
In 1424, Niccolò Delli was sentenced to death for abandoning his post and fled to Siena with his family.
In 1427, the family fled again―this time to Venice.
From 1433 to 1445 he lived in Spain, working in the Court of King John II of Castile, where he was knighted.
His works include the apse cycle in the Old Cathedral of Salamanca.