Born in Akron, Ohio, Seiberling attended the public schools of Akron, and Staunton Military Academy in Virginia. He received his A.B. from Harvard University in 1941, and his LL.B. from Columbia Law School in 1949. During World War II he served in the United States Army from 1942 to 1946. He was then admitted to the New York bar in 1950, and went into private practice.

Seiberling became an associate with New York firm from 1949 to 1954, and then became a volunteer with the New York Legal Aid Society in 1950. He served as a corporate attorney in private industry from 1954 to 1970. During this time he was a member of the Tri-County Regional Planning Commission, Akron, Ohio, from 1964 to 1970.

Seiberling was elected as a Democrat to the Ninety-second and to the seven succeeding Congresses, serving the 14th district from January 3, 1971 to January 3, 1987. He was not a candidate for reelection to the One Hundredth Congress in 1986.

After his time in Congress, Seiberling served as faculty at the law school of the University of Akron from 1992 to 1996. He is currently a resident of Akron.

John Seiberling's cousin, Francis Seiberling, was also a U.S. Representative from Ohio.