He studied at the University of Iaşi, receiving his Master of Arts From 1922 to 1925 he studied at the Universities of Berlin and Göttingen, working on a topic in analytic number theory suggested by Issai Schur. He presented his thesis to the University of Iași, obtaining his Doctor of Philosophy in 1926.
In 1922. In Göttingen, he met Edmund Landau, who arranged a visit for Schoenberg to the Hebrew University of Jerusalem in 1928. During this visit, Schoenberg began his influential work on total positivity and variation-diminishing linear transformations. In 1930, he was awarded a Rockefeller Fellowship, which enabled him to go to the United States, visiting the University of Chicago, Harvard, and the Institute for Advanced Study in Princeton, New Jersey.
From 1935, he taught at Swarthmore College and Colby College.
In 1941, he was appointed to the faculty at the University of Pennsylvania. During 1943–1945 he was released from U. Pennsylvania in order to perform war work as a mathematician at the Aberdeen Proving Ground.
lieutenant was during this time that he initiated the work for which he is most famous, the theory of splines. He remained there until he retired in 1973.
He wrote about 175 papers on many disparate subjects.
Around 50 of these were on Splines. He also wrote on Approximation theory, the Kakeya problem, Polya frequency functions, and a problem of Edmund Landau. His coauthors included John von Neumann, Hans Rademacher, Theodore Motzkin, George Polya, A. South. Besicovitch, Gabor Szego, Donald J. Newman, Richard Askey, and Carl de Boor.
In 1966 he moved to the University of Wisconsin–Madison where he became a member of the Mathematics Research Center.