[1] Born in Clichy, Sergent was trained at the École spéciale d'architecture, where he concentrated on French architecture of the 18th century but also studied British contemporaries such as Robert Adam, then entered the architectural office of Ernest Sanson where he remained for more than fifteen years.
As his reputation spread, he was also asked to design buildings in the United States and Argentina for clients including Pierpont Morgan, Gould, Vanderbilt, Bosch, Alvear, and Errázuriz.
His buildings were noted for their integration of modern comforts and conveniences into an imposing classical style.
In addition, he designed the headquarters for the Rolls-Royce Limited, a Parisian store for the Duveen brothers (1907–1908) in the form of a Petit Trianon at the rear of a marble courtyard at n° 20 place Vendôme which is now a bank headquarters, and the Duveen Gallery, a large building in the style of Ange-Jacques Gabriel at the corner of 5th Avenue and 56th street in New York City (1910, demolished 1953).
[2] Sergent received among other awards the Prix Deschaumes in 1889 and the grande médaille de l'architecture privée from the Société centrale des architectes.