Peck died Sunday at his home in Warren, Conn., longtime friend and Los Angeles publicist Michael Levine said. He had suffered from pancreatic and liver duct cancer.
Born in New York City, Peck received his bachelor's degree from Harvard College in 1958 and his doctorate from the Case Western Reserve University School of Medicine in 1963. He served in the U.S. Army between 1963 and 1972.
Peck spent more than 10 years in the private practice of psychiatry and had his first book "The Road Less Traveled" published in 1978. The self-help book that begins, "Life is difficult," has sold more than 6 million copies in North America and been translated into 20 languages. By the mid-1990s, the book had made 258 appearances on The New York Times best-seller list.
Other books he wrote included "People of the Lie: The Hope For Healing Human Evil," "Meditations From the Road," and "Further Along the Road Less Traveled."
Peck was the recipient of the 1984 Kaleidscope Award for Peacemaking and the 1994 Temple International Peace Prize. He also received The Learning, Faith and Freedom Medal from Georgetown University in 1996.
He is survived by his wife, Kathleen Kline Yates Peck; his daughter, Belinda; his son, Christopher; and two grandchildren.