From the 16th century, the Palau underwent various expansions and transformations in accordance to the necessities of each historic period. The main façade, for instance, is Renaissance style and was designed by the artist Pere Blai. The Orange Tree Courtyard and the Golden Chamber, two of the most emblematic features of the building, are also of the same artistic style.

After the War of Succession, the imposition of the Nova Planta Decrees in 1716 by Spain's King Phillip V brought about the abolition of the General Council and the subsequent occupation of its headquarters by the Real Audienca, or Royal Audience. In 1734 and 1768 the building underwent a series of alterations during the Audiencia's occupation, including an expansion of its chapel and the Gothic building as well as the addition of a crown atop the bell tower, among other reforms.

The Provincial Council began to reside in the Palau in 1822, sharing it first with the Audiencia until 1908 and then with the Mancomunitat, or Commonwealth, of Catalonia from 1914 until it was outlawed in 1925. The changes gave way to an expansion and conversion as well as a redistribution of some of the rooms with the construction of new walls. The period saw the construction of the current staircase, by the architect Romà Prats Montlló and the equestrian statute of Sant Jordi (Saint George) by Andre Aleu Teixidor, added to the Pere Blai façade.

In more recent times, the Palau de la Generalitat remained without significant changes, given the complex historical situation which delayed the introduction of modern and avant-garde art. However, during the seventies more than hundred pieces were acquired, mostly figurative art. Later on, pieces by contemporary artists such as Antoni Clavé, Joan Hernández Pijuán or Antoni Tàpies helped to beautify the rooms of the Catalan Government's headquarters.

Among others, notable pieces include paintings by Joaquín Torres-Garcia (1912-1916), in the room that bears his name; the bust of Enric Prat de la Riba, by Joan Borrell (1918), the Pati dels Tarongers (Orange Tree Courtyard); paintings by Gudiol Montserrat (1974), Jordi Alumà (1976 in the Old Archives Rooms) and Antoni Tà pies (1989, in the Executive Council Meeting Room); the Sant Jordi bronze sculpture by Frederic Seas (1976, Sant Jordi's Hall); J.M. Subirachs's Relief (1976), the entrance to the neo-Gothic bridge connecting the Palau with Presidential Residence or House of the Canons; and the busts of presidents Francesc Macià (1983) and Lluís Companys (1990), made by the same sculptor.