Diane Kaplan was an editor of the Yale Law Journal during law school. After graduation, she clerked for the Honorable Hubert L. Will of the U.S. District Court for the Northern District of Illinois and practiced at the Chicago law firm of Mayer, Brown & Platt. Her litigation experience includes state and federal commercial, criminal, Native American, health, mental health, and juvenile law. Professor Kaplan is a member of numerous bar and professional associations including the Illinois State Bar, the State Bar of California, the District of Columbia Bar, the Federal Trial Bar for the Northern District of Illinois, and the American Bar Association.

In 1996, she was invited to teach Corporations and Civil Procedure as a visiting professor at Boston University School of Law. In 1999, 2004, 2006, and 2014, she presented papers on juvenile and women's law topics at Oxford University in England. She has had five visitorships, four in Beijing and Chanchu, China, where she taught American Constitutional Law and one at Boston University Law School where she taught Civil Procedure and Corporations. She has published more than 31 articles and books in the areas of civil procedure, juvenile, corporate, and constitutional law. Her first book, An Introduction to the American Legal System, was the first American law textbook that was an official publication of the People’s Republic of China. Professor Kaplan joined the faculty in 1983. She teaches Children in the Legal System, Civil Procedure I, and Corporations.