In 1877 he was appointed assistant curator of the section of Oriental antiquities in the United States National Museum, and had charge of an exhibit of biblical archaeology at the centennial exposition of the Ohio valley in 1888.

[3] He was a commissioner for the world's Columbian exposition to the Orient in 1890, and he passed sixteen months in Turkey, Syria, Egypt, Tunis, Algiers, and Morocco securing exhibits.

[3] For a number of years he was employed by the Smithsonian Institution at Washington, with a focus on archaeology and Semitics, serving as the Librarian from December 1, 1892 to 1905.

He was president of Dropsie College for Hebrew and Cognate Learning from 1908 to 1940 and Chancellor of the Jewish Theological Seminary of America.

Adler was an editor of the Jewish Encyclopedia and in collaboration with Allen Ramsay wrote Tales Told in a Coffee House (1898).