The film is set in Venice in the 18th Century. Giacomo Casanova (Heath Ledger), the heart-breakers in the city, spends the greater part of his life in the beds of beautiful women, and his reputation as a passionate seduction artist more than fair.
But the Inquisition is not satisfied with dazzling life Casanovas, from which the nuns are not sure. So it is a day of Doge (Tim McInnery), a serious ultimatum: Either Casanova marries even before the carnival ends, or he will be forever banished from the city. Reluctantly Endorses Casanova on the search for a suitable bride and decide finally for the lovely Victoria (Natalie Dormer), in Venice for their innocence known.
But as Casanova falls on the head neck in Francesca Bruni (Sienna Miller), an emancipated scientist, nothing of a man holding of every night in a different bed and instead spends for the true love fights. Moreover, Francesca has already promised to another man. Casanova leaves unturned to Francesca heart to win, but the Inquisition, headed by Bishop Pucci (Jeremy Irons), it is already close to the heels. As Casanova finally yet heard of Francesca, seems already to be too late for the two. But they have not reckoned with Giacomo mother who has promised one day to return to Venice, and then the story but still a good end.