He graduated from high school (Abitur) in 1966, and studied history and Latin between 1966 and 1971 at the Rheinische Friedrich-Wilhelms-Universität Bonn and the Philipps-Universität Marburg.

He received his doctorate in 1975 in Bonn, his dissertation, Die Entstehung von Domkapiteln in Deutschland, supervised by Eugen Ewig.

His habilitation, for Die Entstehung des päpstlichen Investiturverbots für den deutschen König, took place in 1979 at the University of Regensburg.

In 1980 he was appointed professor of medieval and modern history at the Rheinische Friedrich-Wilhelms-Universität Bonn, and in 1994 went to the Ludwig-Maximilians-Universität München to take charge of the MGH.

Schieffer's specialism was the political, legal, and religious history from the late antique to the high middle ages, and particularly the era of the Carolingians.