He was born in Indianapolis in 23 March 1941 to Julia Goldberger Kwitny and Dr. I. J. Kwitny (president of the medical staff at St. Vincent Indianapolis Hospital), and graduated in 1962 from the University of Missouri's School of Journalism. He received a master's degree in history in 1964 at New York University. His newspaper career began as a reporter for The Evening News (of Perth Amboy) between 1963 & 1969. He was a former front page feature writer for the Wall Street Journal producing front-page columns and articles about national and international topics; he joined the Journal in 1971 and worked there for the next seventeen years. He stayed with The Journal until his move to PBS in 1988. More recently, he worked for the Gannett Company guiding Trenton coverage for its New Jersey papers. He also served as a consultant on Pope John Paul II for NBC Nightly News. Kwitny also had in the 1980s a PBS series entitled The Kwitny Report which during its four year run won the George Polk award (in 1990) for best investigative reporting on television.

He is also the author of a number of non-fiction books. His fifth book (Endless Enemies) received a Pulitzer Prize nomination.

He was married in 4 September 1993 under Catholic rites to a then-Methodist poet Wendy Wood Kwitny (his second marriage; his first wife, Martha Kaplan Kwitny, had previously died of long-term kidney disease at the age of 33), Kwitny devoted some years to completing his biography of Pope John Paul II, which he began in 1992. He died in 1998 of esophageal stomach cancer in Memorial Sloan-Kettering Cancer Center, aged 57. "He was survived by his second wife and their two sons and two daughters from his first marriage. His first wife died in 1978."