The son of a rabbi, Segal attended Midwood High School in Brooklyn and traveled to Switzerland to take summer courses. He attended Harvard College, graduating as both the class poet and Latin salutatorian in 1958, after which he obtained his master's degree (in 1959) and a doctorate (in 1965) in comparative literature, from Harvard University.
Segal was a professor of Greek and Latin literature at Harvard University, Yale University, and Princeton University. He had been a Supernumerary Fellow and subsequently an Honorary Fellow of Wolfson College at Oxford University.
His first academic book, Roman Laughter: The Comedy of Plautus, revolutionized the great Roman comic playwright best known today as the inspiration for the Broadway hit, A Funny Thing Happened on the Way to the Forum. In 2001 Harvard published his The Death of Comedy, the all-encompassing literary history.
In 1967, from the story by Lee Minoff, he was one of the writers of the screenplay for The Beatles' 1968 motion picture, Yellow Submarine.
In the late 1960s, Segal collaborated on other screenplays, and also had written a synthetic romantic story by himself about a Harvard student and a Radcliffe student, but failed to sell it. However, literary agent Lois Wallace at the William Morris Agency suggested he turn the script into a novel and the result was a literary and motion picture phenomenon called Love Story. A New York Times No. 1 bestseller, the book became the top selling work of fiction for 1970 in the United States, and was translated into 33 languages worldwide. The motion picture of the same name was the number one box office attraction of 1970.
Segal went on to write more novels and screenplays, including the 1977 sequel to Love Story, called Oliver's Story.
He published a number of scholarly works as well as teaching at the university level. He acted as a visiting professor for the University of Munich, Princeton University, and Dartmouth College. He wrote widely on Greek and Latin literature. His novel The Class (1985), a saga based on the Harvard Class of 1958, was also a bestseller, and won literary honour in France and Italy. Doctors was another New York Times bestseller from Segal.
Segal was an accomplished competitive runner. He was a sprinter at Midwood High School, and ran the 2 mile at Harvard College. He began marathon running during his second year at Harvard, when track and field head coach Bill McCurdy was impressed with how fast he had run ten miles. Segal ran in the Boston Marathon almost every year from 1955 to 1975. He finished in 79th place at 3 hours, 43 minutes in his first attempt, and his best performance was in 1964 when he finished 63rd with a time of 2:56:30. He recounted that after one Boston marathon someone yelled "Hey, Segal, you run better than you write".
Segal covered the marathon as a color commentator for telecasts of both the 1972 and 1976 Summer Olympics for the American Broadcasting Company (ABC). His most notable broadcast was in 1972 when he and Jim McKay called Frank Shorter's gold-medal-winning performance. When an impostor, West German student Norbert Sudhaus, ran into Olympic Stadium ahead of Shorter, an emotionally upset Segal screamed, "That is an impostor! Get him off the track!...This happens in bush league marathons!...Throw the bum out!...Get rid of that guy!" Moments later he personalized his on‑air remarks by saying, "Come on, Frank! You won it!...It's a fake, Frank!" Amby Burfoot called Segal's account "one of the most unprofessional, unbridled, and totally appropriate outbursts in the history of Olympic TV commentary", taking into consideration the fact that Segal had taught Shorter at Yale. In 2000, The Washington Post included the phrase among the ten most memorable American sports calls.
Segal was married to Karen Marianne James from 1975 until his death; they had two daughters, Miranda and Francesca Segal. Francesca, born in 1980, is a freelance journalist and literary critic and currently The Observer's Debut Fiction columnist.
Segal, who suffered from Parkinson's disease, died of a heart attack on January 17, 2010, and was buried in London. In a eulogy delivered at his funeral, his daughter Francesca said, "That he fought to breathe, fought to live, every second of the last 30 years of illness with such mind-blowing obduracy, is a testament to the core of who he was – a blind obsessionality that saw him pursue his teaching, his writing, his running and my mother, with just the same tenacity. He was the most dogged man any of us will ever know."Yellow Submarine (1968)
The Games (1970)
R. P. M. (1970)
Love Story (1970)
Jennifer on My Mind (1971)
Oliver's Story (1978)
A Change of Seasons (1980)
Man, Woman and Child (1983)
Acts of Faith (1992)