The building was originally designed by Gian Lorenzo Bernini for the young Cardinal Ludovico Ludovisi, nephew of Pope Gregory XV.

However, with the death of Gregory XV by 1623, work stopped, and was not restarted until the papacy of Pope Innocent XII (Antonio Pignatelli), when it was completed by the architect Carlo Fontana, who modified Bernini's plan with the addition of a bell gable above the main entrance.

With the Unification of Italy in 1861 and the transfer of the capital to Rome in 1870, Montecitorio was seized by the Italian government and chosen as the seat of the Chamber of Deputies, after consideration of various possibilities.

Basile also added the so-called Transatlantico, the long and impressive salon which surrounds the debating chamber and now acts as the informal centre of Italian politics.

The debating chamber is characterized by numerous decorations in the Art Nouveau style: the impressive canopy of coloured glass (the work of Giovanni Beltrami), the pictorial frieze entitled The Italian People (by Giulio Aristide Sartorio) which surrounds the chamber, the bronze figures flanking the presidential and government benches, and the panels depicting The Glory of the Savoy Dynasty by Davide Calandra.