Sargent was born in Philadelphia, Pennsylvania. He graduated from Upper Darby High School in 1945. As of 2006, he is one of 35 alumni to be on the school's Wall of Fame.
Sargent began writing for television in 1953 and through the 1960s he scripted episodes for Route 66, Ben Casey and The Alfred Hitchcock Hour. He collaborated on his first screenplay for a motion picture in 1966 and gained recognition for I Walk the Line and Paper Moon for which he won the WGA Award for Best Screenplay Based on Material from Another Medium and was nominated for an Academy Award. He won the Academy Award for Adapted Screenplay in 1978 for the film Julia and again in 1981 for Ordinary People. He collaborated on the 2004 screenplay for Spider-Man 2 and Spider-Man 3 released in 2007.
