His work was influenced by his cultural and religious roots at a time when many of his German Jewish contemporaries chose to convert to Christianity.

Oppenheim is considered by the scholar Ismar Schorsch to be in sympathy with the ideals of the Wissenschaft des Judentums movement, because he remained "fair to the present" without denying his past.

Later he visited Paris, where Jean-Baptiste Regnault became his teacher, and then went to Rome, where he studied with Bertel Thorwaldsen, Barthold Georg Niebuhr, and Johann Friedrich Overbeck.

In 1825 he settled at Frankfurt, and shortly after exhibited his painting David Playing Before Saul, to see which a great number of admirers from all parts of Europe visited his studio.

His Return of the Jewish Volunteer is among his most famous works and was frequently reproduced; others include Mignon and the Harper, Italian Genre Scene, Confirmation, and Sabbath Blessing.