In March 1849 Russell was appointed by Lord Malmesbury as attaché at Vienna. From 1850 to 1852 he was temporarily employed in the foreign office, whence he passed to Paris. He remained there, however, only about two months, when he was transferred to Vienna. In 1853 he became second paid attaché at Paris, and in August 1854 he was transferred as first paid attaché to Constantinople, where he served under Lord Stratford de Redcliffe. He had charge of the embassy during his chief's two visits to the Crimea in 1855, but left the East to work under Lord Napier at Washington in 1857. In the following year he became secretary of legation at Florence, but was detached from that place to reside in Rome, where he remained for twelve years, until August 1870. During all that period he was the real though unofficial representative of Britain at the Vatican. Russell's personal success with Otto von Bismarck led to his appointment as ambassador at Berlin in October 1871. He admired the new Germany and liked Germans: during his thirteen years in Berlin he never forfeited the confidence of Bismarck. Just as he had understood his Constantinople chief, Stratford de Redcliffe, and had never been broken by his suspicious rages, so too he achieved a sympathetic understanding of Bismarck. He withstood the Iron Chancellor's rages about real or imaginary plots, dispelled his darkest suspicions of British policy, and penetrated to the core of Bismarckian motives and strategy. For example, he reported to London in October 1872 how Bismarck's plans for a Kulturkampf were backfiring by strengthening the ultramontane position inside German Catholicism: Russell was trusted by Victoria, the Crown Princess and the Hohenzollerns, but his cordiality to Bismarck's enemies was never tainted by the suspicion of intrigue. Nor was the objectivity of his dispatches compromised by his private belief that Kulturkampf must fail, or by his revulsion at Bismarck's persecution of Roman Catholicism. From the outset, he recognised Germany's colonial aspirations, though his appreciation of this complex situation was imperfect. In 1879 he was responsible for the novelty of attaching a commercial expert to the Berlin embassy staff. After his eldest brother became eventually 9th Duke of Bedford in 1872, Russell was granted the rank of a younger son of a duke, becoming known as Lord Odo Russell. He was sworn of the Privy Council the same year. He was subsequently made a Knight Grand Cross of the Order of the Bath in 1874, a Knight Grand Gross of the Order of St Michael and St George in 1879, and raised to the peerage as Baron Ampthill, of Ampthill in the County of Bedford, in 1881. He was British delegate at the Congress of Berlin in 1878, along with Disraeli and Salisbury.
Ampthill, Odo William Leopold Russell Baron, and Noel Blakiston. The Roman question: extracts from the despatches of Odo Russell from Rome, 1858-1870
Knaplund, Paul, ed. Letters from the Berlin Embassy, 1871–1874, 1880–1885
Taffs, Winifred. "Conversations between Lord Odo Russell and Andrássy, Bismarck and Gorchakov in September, 1872." Slavonic and East European Review : 701-707.