Born in Lucca, he was mostly active in Venice and Rome, where he became a member of the large studio of Pietro da Cortona, often working closely with Giovanni Coli. With Coli, Gherardi was initially a trainee of Pietro Paolini in Lucca. One of his masterpieces are the ceiling frescoes in the Palazzo Colonna in Rome, celebrating the participation of a family member in the Battle of Lepanto.
In Venice, Coli and Gherardi also completed frescoes (1670–72) of the dome of the church of San Nicolò da Tolentino with a fresco of the Glory of San Nicola and in the church of San Pantalon. In Venice, Coli and Gherardi frescoed the Library of St George.