Paolo Albiani and his ally Pietro want the plebeian Simon Boccanegra to be elected doge. Boccanegra is persuaded to take the position. Paolo notes that the noble Fiesco, who until now felt it was below his rank that his daughter should be the wife of a sailor, will gladly add Maria, by whom Boccanegra had a child, to a doge. Grief-stricken Fiesco leaves his palace, Maria is dead. Boccanegra arrives and offers a truce. Fiesco would accept this if the man entrusted her with the upbringing of his grandson. Boccanegra sadly admits that the little girl has disappeared.
Twenty-five years passed, the Doge exiled his enemies. Among them was Fiesco, who now lives under the name Andrea. Amelia, adopted by the family, lives in the Grimaldi palace. The girl is waiting for her love, Gabriele Adorno. He is afraid that the doge wants to give him to Paolo, so he urges their reconciliation. Fiesco tells Adorno that Amelia is not of noble birth, but the boy does not care. Fiesco blesses their marriage. The Doge arrives, to whom Amelia honestly reveals that she is in love and will not marry Paolo. He also says that he was adopted and that the only memory he has of his mother is a picture of her face. Boccanegra realizes that Amelia is none other than his long-lost daughter...
