Toobin was born in New York City, New York., the son of former ABC News and CBS News correspondent Marlene Sanders. He attended Columbia Grammar and Preparatory School, in New York City and attended Harvard College where he covered sports for The Harvard Crimson, using the column name "Inner Toobin." He graduated magna cum laude with a Bachelor of Arts degree in 1982 and earned a Truman Scholarship. He is also a 1986 magna cum laude graduate of Harvard Law School, where he was an editor of the Harvard Law Review.
Toobin began freelancing for The New Republic as a law student. He went on to become a law clerk to a federal judge and work as an associate counsel to Independent Counsel Lawrence E. Walsh during the Iran-Contra affair and Oliver North's criminal trial, before becoming an Assistant U.S. Attorney in Brooklyn. He then took up his post in 1993 at The New Yorker, and became the first television legal analyst in 1994, at ABC.
He currently is a staff writer at The New Yorker, a senior analyst for CNN since 2002, and the author of five books. Toobin's latest book, The Nine: Inside the Secret World of the Supreme Court, has received awards from the Columbia Graduate School of Journalism and the Nieman Foundation for Journalism at Harvard University. His first book, Opening Arguments: A Young Lawyer's First Case...United States v. Oliver North, an account of his work for Lawrence Walsh, was released after winning a lawsuit against Walsh, who opposed its publication. Toobin was criticized for the book on ethical grounds by some experts on ethics and by a New York Times editorial.
In 1994, Toobin broke the story in The New Yorker that the O. J. Simpson legal team planned on accusing Mark Furhman of planting evidence and playing "the race card." In 2003, he secured the first interview with Martha Stewart in regards to the charges against her for insider trading.
Toobin has provided broadcast legal analysis on many high profile cases, including Michael Jackson, the O.J. Simpson civil trial and the Starr investigation of President Clinton. He received a 2000 Emmy Award for his coverage of the Elián González custody saga.
Toobin is a longtime friend of Supreme Court justice Elena Kagan, having met her while the two were students at Harvard Law School. He has described Chief Justice John Roberts as "very, very conservative."
In March 2009, Politico revealed that Toobin was a member of the private discussion group JournoList, where "several hundred left-leaning bloggers, political reporters, magazine writers, policy wonks and academics" "talked stories and compared notes."