Before joining Washburn Law, Professor Mastrosimone was an adjunct professor at the University of Kansas Law School and at the George Washington University Law School where he taught courses in legal research and writing. For more than a decade he has dedicated his career to labor and employment law while working for government agencies and law firms. He served as the Chief Legal Counsel for the Kansas Human Rights Commission and as Senior Legal Counsel to the former chairman of the National Labor Relations Board. He also practiced with Stinson Morrison Hecker and Crowell & Moring where he counseled management on labor and employment matters and represented management in labor and employment litigation.

Professor Mastrosimone received his J.D., with highest honors from The George Washington University Law School where he was a notes editor of The George Washington University Law Review, the recipient of the Ogden W. Fields Labor Law Award and the Lawrence E. Siebel Memorial Prize for employment law, and a member of the Order of the Coif. He is licensed to practice law in Kansas, Missouri, Virginia, and Washington, D.C. Professor Mastrosimone's scholarly interests include legal education, acquisition of client counseling skills, employment law, and labor law.