He has made charitable contributions to the DePaul University College of Law, Columbia University Medical Center, the Weill Cornell Medical College of Cornell University, the Tufts University School of Medicine, the Metropolitan Museum of Art, the Art Institute of Chicago, and the Metropolitan Opera. He was the founder of FAITH: An Endowment for Orthodoxy and Hellenism. He also served as Trustee Emeritus of Tufts University and Chairman of the Board of Overseers for the School of Medicine of Tufts University; member of the Columbia University Medical Center Board of Visitors; member of the Board of Overseers of the Weill Cornell Medical College and Graduate School of Medical Sciences. He sat on the Board of Directors of the Onassis Public Benefit Foundation, and he was Vice Chairman of the Greek Orthodox Archdiocese of America. In 1986, Jaharis and wife Mary Jaharis founded the Jaharis Family Foundation, Inc. In 2013, the Foundation pledged $2 million to help relieve hunger and poverty in Greece during the country's fiscal crisis.