His father, Isaac Bernays (1792-1849), a man of wide culture, was the first orthodox German rabbi to preach in the vernacular. Jakob studied from 1844 to 1848 at the university of Bonn, the philological school of which, under Welcker and Ritschl (whose favourite pupil Bernays became), was the best in Germany.
In 1853 he accepted the chair of classical philology at the newly founded Jewish theological college (the Frankel seminary) at Breslau, where he formed a close friendehip with Mommsen. In 1866, when Ritschl left Bonn for Leipzig, Bernays returned to his old university as extraordinary professor and chief librarian. He remained at Bonn until his death on the 26th of May 1881. His chief woiks, which deal mainly with the Greek philosophers, are:
See notices in Biographisches Jahrbuch für Alterthumskunde (1881), and Allgemeine deutsche Biographie, xlvi. (1902); art, in Jewish Encyclopaedia; also Sandys, Hist, of Class. Schol. iii. I 76 (1908).