Joseph Unger was born in Vienna into a Jewish family that converted to Christianity. Unger was baptized while very young. He was educated and studied law in Vienna and achieved his Ph.D. from the University of Koenigsberg (1850) and Doctor of Law from the University of Vienna (1853). In 1855 he was appointed Assistant Professor and Full Professor at the University of Vienna in1871. Unger worked with Julius Glaser in writing The Classics of Austrian Jurisprudence. Joseph Unger was also known for his contribution to civil jurisprudence.
From 1871 to 879 he served as Minister without portfolio and President of Reichsgericht, from 1880 to 913.
He is considered the first Austrian jurist to use scientific methods to Austrian Civil Law. He was a prolific writer. Among his more important works are two volumes of System des Oesterreicischen Privatrechts, in which he showed the development of legal institutions.