Originally a cellist, he began his career as opera conductor after having participated as cellist in the world premiere of Verdi's Otello at La Scala in 1887 under the composer's supervision. Toscanini's ability to interpret his scores impressed the composer.
From 1898 to 1908 Toscanini was resident conductor at La Scala, Milan. Outside of Europe, he conducted at the Metropolitan Opera in New York (1908–1915) as well as The New York Philharmonic Orchestra (1926–1936). Toscanini was the first non-German conductor to appear at Bayreuth (1930–1931). In the 1930s he conducted at the Salzburg Festival (1934–1937) and the inaugural concert in 1936 of the Palestine Symphony Orchestra (now the Israel Philharmonic Orchestra) in Tel Aviv.
He took the Scala Orchestra to the United States on a concert tour in 1920-21; Toscanini made his first recordings for the Victor Talking Machine Company.
Though he ran in 1919 unsuccessfully as a Fascist parliamentary candidate in Milan and had been called "the greatest conductor in the world" by Mussolini, he became disillusioned with fascism and left for the United States where the NBC Symphony Orchestra was created for him in 1937.
During a concert on April 4, 1954, in Carnegie Hall, Toscanini suffered a memory lapse caused by a transient ischemic attack. He never conducted live in public again. Toscanini was 87 years old when he retired.