His first important project was an apartment building on rue Franklin in Paris (1903), where the concrete structure, instead of being concealed, was clearly visible and was a part of the exterior design.

He made an even more radical experiment with the construction of a garage on rue de Ponthieu (1906) (now destroyed) with a simplified cubic structure expressing the interior, large bays of windows and a lack of decoration, which resembled the later International Style.

[2] His most famous building was the Théâtre des Champs-Élysées a project which he took over from the Art Nouveau architect Henry van de Velde.

The interior decoration featured works by the modernist artists of the day; a dome by Maurice Denis, paintings by Édouard Vuillard and Jacqueline Marval, and a stage curtain by Ker-Xavier Roussel.

[2] In his later works, Perret used concrete in imaginative ways to achieve the functions of his buildings, while preserving classical harmony, symmetry and proportions.

His last major work, finished after his death, was the St. Joseph's Church, Le Havre, (1951–58) whose most prominent feature is its tower, like a lighthouse, 107 meters high, and visible at sea.

[3] Among the many young architects who worked in the office of Perret from 1908 to 1910 was Charles-Édouard Jeanneret-Gris, who later became known as Le Corbusier; it was his first experience in an architectural firm.