A great-grandson of Aleksandr Danilovich Menshikov, Duke of Ingria, and a cognatic descendant of the Princely House of Galitzine (another of his great-grandfathers was Prince Michael Golitsyn, the military governor of Åbo during the Russian occupation in the Great Northern War). Aleksandr entered the Russian service as attaché to the embassy at Vienna in 1809. He became close with Tsar Alexander I and accompanied him throughout his campaigns against Napoleon. In 1817, Menshikov was appointed acting Quartermaster general of the General Staff. In 1823, he was transferred to the ministry of foreign affairs. Menshikov retired from army service in 1824.