Alexandre's father Nicholas Benois and brother Leon Benois were prominent Russian architects. Alexandre didn't plan to devote his life to art and graduated from the Faculty of Law, St. Petersburg University in 1894. Three years later, while in Versailles, he painted a series of watercolors depicting Last Promenades of Louis XIV. When exhibited by Pavel Tretyakov in 1897, they brought him to attention of Sergei Diaghilev and Leon Bakst. Together they founded the art magazine Mir iskusstva which aimed at promoting Art Nouveau in Russia.

During the first decade of the new century, Benois continued to edit Mir iskusstva but also pursued his scholarly interests. He prepared and printed several monographs on the 19th-century Russian art and Tsarskoye Selo. From 1918 to 1926, he ran the gallery of Old Masters in the Hermitage Museum, to which he secured his brother's heirloom - Leonardo's Madonna Benois. In 1903, he printed his illustrations to Pushkin's Bronze Horseman which have since been recognized as one of the landmarks in the genre.

In 1901, Benois was appointed scenic director of the Mariinsky Theatre. Since then, he devoted most of his time to stage design and decor. Les Sylphides (1909), Giselle (1910), and Petrushka (1911) are counted among his greatest triumphs. Although he worked primarily with Diaghilev for the Ballets Russes, he simultaneously collaborated with the Moscow Art Theatre and other notable theatres of Europe. His Memoirs were published in two volumes in 1955. The Russian artists Eugene Lanceray and Zinaida Serebryakova were his nephew and niece, and the British actor Sir Peter Ustinov was his grand nephew.