In 1970 Di Fabio began as a local government official in middle service in Dinslaken.

[2] After completing the two state examinations in law in 1982 and 1985, Di Fabio was a judge at the Duisburg Social Court.

[2] In 1986 he worked as a wissenschaftlicher Mitarbeiter (scientific assistant) at the Institute for Public Law at the University of Bonn.

[2] In 1987, he achieved there his dissertation Rechtsschutz im parlamentarischen Untersuchungsverfahren, followed by a doctorate in the subject of social sciences in 1990.

[4][3] In April 2020, Di Fabio was appointed by Minister-President Armin Laschet of North Rhine-Westphalia to a 12-member expert group to advise on economic and social consequences of the COVID-19 pandemic in Germany.