Warren joined the University of Pennsylvania Law School as a full professor in 1987 and obtained an endowed chair in 1990, becoming the William A. Schnader Professor of Commercial Law. In 1992, she taught for a year at Harvard Law School as Robert Braucher Visiting Professor of Commercial Law. In 1995, Warren left Penn to become Leo Gottlieb Professor of Law at Harvard Law School. In 1996 she became the highest-paid professor at Harvard University who was not an administrator, with a $181,300 salary and total compensation of $291,876, including moving expenses and an allowance in lieu of benefits contributions. , she was Harvard's only tenured law professor who had attended law school at an American public university. Warren was a highly influential law professor. She published in many fields, but her expertise was in bankruptcy and commercial law. From 2005 to 2009 Warren was among the three most-cited scholars in those fields.