Weissmann was born in Vienna, Austria on August 7, 1930, to Adolf and Greta Weissmann. He immigrated to the United States in 1938, and became a naturalized American citizen in 1943. After the Bronx High School of Science, he received a B.A. from Columbia University in 1950 and his M.D. from New York University in 1954. He also pursued an early career in art, exhibiting at a major New York gallery.
After clinical training at the Mt. Sinai Hospital, New York in New York City and active service as captain in the U.S. Army Medical Corps, he took a research fellowship in the Department of Biochemistry at NYU (1958–59) under Nobel laureate, Severo Ochoa. Lewis Thomas then selected him as Chief Medical Resident at Bellevue Hospital Center (1959–60). Weissmann next worked at the Strangeways Research Laboratory, Cambridge England, studying cell biology under Dame Honor B. Fell to 1962. He returned to N.Y.U. School of Medicine, and has been on its faculty to date. In 1964 and 1969, he was a visiting investigator at the Babraham Institute|(Cambridge), England; in 1973-1974 he was awarded a Guggenheim Foundation scholarship at the Centre de Physiologie et d'Immunologie Cellulaires, Hôpital Saint-Antoine|Hopital Saint Antoine, Paris, as a visiting investigator; and as visiting fellow at the William Harvey Research Institute], London in 1987.
Weissmann became Professor of Medicine at N.Y.U. in 1970, and served as Director of the Division of Rheumatology from 1973 to 1999. From 1970 to date, he has spent summers as an investigator and lecturer and has served for 18 years as a trustee (now emeritus) at the Marine Biological Laboratory Woods Hole, MA He is best known for having presented evidence that rheumatoid arthritis is an immune complex disease (provoked perhaps by genetic programs that misdirect immune responses to oral bacteria). His laboratory found that crises in Systemic Lupus Erythematosus are provoked by intravascular complement activation. He has also pioneered studies in leukocyte activation (via C5a, immune complexes, etc.), the role of salicylates and corticosteroids in cell signalling and adhesion (MAP kinases, erk 1-2, MEK, NFKappaB).
He is responsible for the codiscovery of Liposomes in 1965 and credited with coining that name by the Oxford Dictionary of the English Language (1965). He was a founder (with E.C. Whitehead) and a director of the Liposome Company, Inc. from 1982 to 2000, and two drugs based on his liposome work are now in the clinic (Abelcet and Myocet). There are now over 52,000 references to liposomes on PubMed. Dr. Weissmann has received the Lila Gruber Award for Cancer Research two residencies at the Rockefeller Foundation Study Center at Bellagio, the Allesandro Robecchi and Paul Klemperer awards for inflammation research, as well as the Distinguished Investigator and Presidential Gold Medal Awards of the American College of Rheumatology He is a foreign member of the Accademia Nazionale dei Lincei of Rome and the Royal Society of Medicine of London. He is a Master and past president of the American College of Rheumatology, a past president of the Harvey Society, a Fellow of the AAAS, The New York Academy of Medicine and The New York Academy of Sciences. With the late Joshua Lederberg, he was a founding member of the advisory boards of the Pew Scholars in Biomedical Sciences, the Ellison Medical Foundation and was the founding chairman of the jury for the Prix Galien Prix Galien USA.
From 1975-2001, Weissmann was the founding editor of the journal, Inflammation; he edited MD Magazine from 1979-1984, and from 2006 to 2016 has served as the Editor-in-Chief of The FASEB Journal.
A member of PEN, his essays and reviews of cultural history have been published in The New Republic, the London Review of Books, and The New York Times Book Review, and have been collected in ten volumes,from The Woods Hole Cantata (1985) to Epigenetics in the Age of Twitter: Pop Culture and Modern Science (2012).His work has been praised for scientific insight by Jonas Salk, for literary style by Kurt Vonnegut, and for breadth of general culture by Adam Gopnik. His published volumes of essays include:The Woods Hole Cantata (1985) ISBN 9780396086185
They All Laughed At Christopher Columbus (1987) ISBN 9780812916188
The Doctor With Two Heads (1990) ISBN 9780679733911
The Doctor Dilemma (1992) ISBN 9781879736054
Democracy and DNA (1995) ISBN 9780809093052
Darwin's Audubon (2002) ISBN 9780738205977
The Year of the Genome (2002) ISBN 9780805072921
Galileo's gout : Science in an age of Endarkenment (2007) ISBN 9781934137000
Mortal and Immortal DNA (2009) ISBN 9781934137161
Epigenetics in the Age of Twitter (2012) ISBN 9781934137390
He has been married to Ann (Raphael) Weissmann since 1953, and has two children, Lisa Beth Weissmann, MD of Mount Auburn Hospital Cambridge, MA and Andrew Weissmann, Esq. of the U.S. Department of Justice in Washington, D.C.