Blumenthal was the chair of the UC Santa Cruz Academic Senate from 2001 to 2003 and served one year each as Vice Chair and Chair of the University of California Academic Senate. He succeeded Denice Denton as UCSC chancellor in 2006 after her suicide. Blumenthal step down as chancellor at the end of June 2019 to resume work in Astronomy and to work part time at the U.C. Berkeley Center for Studies in Higher Education. He was succeeded as chancellor by Cynthia Larive.