His family credited the palace's floor plan to two anonymous French architects, but the design of the main building is officially listed as being by the Brazilian José Maria Jacinto Rebelo, a disciple of Grandjean de Montigny and one of the main architects active in the period.

Some structures around the courtyard were renovated between 1927 and 1930 by the French architect Joseph Gire, the Scotsman Robert Prentice and the Austrian Anton Floderer, in a neoclassical Beaux-Arts style.

[2] Through a project that won a competition promoted by the Brazilian Institute of Architects, Robert Prentice and Anton Floderer designed the library, which was built between 1928 and 1930 to store the archives and maps donated to the government by the Baron of Rio Branco.

The relationship established between Brazilian diplomacy and the palace they occupied for seven decades led to the term Itamaraty becoming the official cognomen of the ministry.

It also contains the United Nations (UN) Information Office in Brazil and the Alexandre de Gusmão Foundation's Center for History and Diplomatic Documentation.