After being raised to the rank of Privy Chamberlain supernumerary, Taliani became auditor (May 16, 1869) and chargé d'affaires (1870) of the nunciature to Germany. He was made a Domestic Prelate of His Holiness in 1871, and was sent to the nunciature to France, where he served as auditor from 1875 to 1879. Taliani then entered the service of the Roman Curia upon being named a referendary prelate of the Supreme Tribunal of the Apostolic Signature on March 17, 1880. In 1885, he was made protonotary apostolic participant (March 16) and auditor of the Roman Rota (May 18). He later became vicar of the Archpriest of the Lateran Basilica, Francesco Cardinal Satolli, in 1889.
On June 22, 1896, Taliani was appointed Titular Archbishop of Sebastea by Pope Leo XIII, receiving his episcopal consecration on the following June 29 from Lucido Cardinal Parocchi. He was later named Nuncio to Austria on July 24 of that same year. As Nuncio, he served as both the Pope's representative to and the Vatican's ambassador to that country. Taliani was made a
Pope Leo created him Cardinal Priest of S. Bernardo alle Terme in the consistory of June 22, 1903, ceasing to serve as Nuncio on that same date. Later that year, Taliani participated in the papal conclave which selected Leo's successor, Pope Pius X.