Kornheiser was born and raised to a Jewish family in Lynbrook, New York, on Long Island where he attended George W. Hewlett High School. He was a high school classmate of Jim Steinman, whose works include Air Supply's "Making Love out of Nothing at All."

After graduation he enrolled at Harpur College (now Binghamton University) where he began his journalism career and graduated with a degree in English in 1970. During the summers of his youth, he attended Camp Keeyumah, a summer camp in Pennsylvania. His counselor there was basketball coach Larry Brown.

Kornheiser is the only child of Ira (1910—2000) and Estelle Kornheiser (d. 1968). Kornheiser grew up in a Jewish household, and celebrated his Bar Mitzvah at a Conservative synagogue. Kornheiser currently resides in Washington, D.C., as well as Rehoboth Beach, Delaware, with his wife Karril. They have two children, Michael and Elizabeth.

On August 15, 2006, Kornheiser revealed on The Dan Patrick Show that he had skin cancer and had received treatment.

Politically, Kornheiser describes himself as a "blue state guy." He and Wilbon are good friends with Democratic political advisor James Carville, who has appeared several times on PTI.

Kornheiser began his career in New York City, where he wrote for Newsday between 1970 and 1976, The New York Times between 1976 and 1979, and also worked as a teacher. Kornheiser joined The Washington Post in 1979 as a general assignment reporter in Style and Sports. He became a full-time sports columnist in 1984. He also wrote columns for the Post's Style Section between November 12, 1989, and September 30, 2001.

His columns were usually sarcastic with touches of humor. The most distinct style of his columns is that he often uses his alter ego in italics to question his points of views for self-deprecation, like "Excuse me, Tony..."

In 1991, Kornheiser created a string of now-famous Bandwagon columns to describe the Washington Redskins' Super Bowl run that year. He started the idea when the Redskins trounced the Detroit Lions 45-0. He officially unveiled the first Bandwagon column when the team had an undefeated 4-0 record. From then on, the Bandwagon column appeared weekly. When the Redskins advanced to Super Bowl XXVI, Kornheiser and his Post colleagues Jeanne McManus and Norman Chad rode a thirty-three-foot recreational vehicle decorated as the Bandwagon for a 1,200-mile journey to Minneapolis, Minnesota.

In the 1990s, Kornheiser usually wrote three columns per week, which were a Tuesday column and a Thursday column in the Sports Section and a Sunday column in the Style Section. Because of his work on both radio and Pardon the Interruption, he stopped writing Style Section columns and only wrote one column a week. His last Style Section column was published on September 30, 2001. His three books, Pumping Irony, Bald as I Wanna Be and I'm Back for More Cash, are the compilations of his Style Section columns.

Kornheiser was a finalist for the 1997 Pulitzer Prize for Commentary.

He also started working for ESPN in 1997 and kept his column at the Post. As part of his ESPN Radio contract, Kornheiser wrote columns called Parting Shots for ESPN The Magazine between 1998 and 2000.

In 2005, Kornheiser started to write short columns called A Few Choice Words with his photo in the Post's Sports Section. These short, sports-related columns appeared on the second page of the Post's Sports section and were much shorter than the full-length columns Kornheiser used to write for the paper. This was the first time that the Post displayed a columnist's photo beside his column. He called these short columns "columnettes." He usually wrote three "columnettes" per week unless he had other duties. He did not write columns between April 26, 2006, and August 7, 2006, to prepare as an analyst of ESPN's Monday Night Football.

Starting August 8, 2006, he wrote columns called Monday Night Diary to describe his adventures on Monday Night Football. His short-column space was later replaced by Dan Steinberg's D.C. Sports Bog.

On May 14, 2008, it was announced that Kornheiser had accepted a buyout from the Post. "I love the paper. They were great to me every day that I was there," he told Reuters. "But I don't do much for the paper anymore." Kornheiser had not written a regular column for the paper's print edition since 2006. However, Wilbon and Tony continued to tape a "Talking Points" mini online TV feature for the Washington Post until June 3, 2009 when an installment termed the final one was posted on the Post's site. In it Michael Wilbon says he thinks there will be further installments while Kornheiser seems certain it is a permanent decision management has made.

On May 20, 2010, Kornheiser said on his radio show that in fact he was fired by the Washington Post, saying "they fired me in a despicable way."

He hosted The Tony Kornheiser Show first locally on WTEM, better known as Sports Talk 980, in Washington, D.C. between May 25, 1992, and November 14, 1997. The show was then syndicated by ESPN radio between January 5, 1998, and March 26, 2004. He was back on WTEM locally between November 10, 2004, and April 28, 2006. His show was once carried by XM Satellite Radio between February 28, 2005, and April 28, 2006.

After completing the 2006 season on ESPN's Monday Night Football, Kornheiser signed with WTWP, Washington Post Radio, to relaunch his radio show on February 20, 2007. The show aired live from 8:30 a.m. to 10:30 a.m. and was then replayed from 10:30 a.m. to 12:30 p.m. XM Radio carried his show on a thirty-minute delay, from 9 a.m. to 11 a.m., beginning March 5, 2007, on XM Sports Nation, Channel 144. Kornheiser went on hiatus from the show following the June 28, 2007, broadcast because of his Monday Night Football duties. The show was hosted by David Burd and included the same supporting cast. The show was called The Tony Kornheiser Show Starring David Burd during the hiatus. Kornheiser returned to the show as the full-time host from January 21, 2008, to June 27, 2008. The show aired live from 8:00 a.m. to 10:00 a.m. and was replayed from 2:00 p.m. to 4:00 p.m on WWWT, and on XM Sports Nation, XM channel 144 from 8:15 a.m. to 10:00 a.m. He announced during this period in 2008 that he would not be back on the radio until he was done with Monday Night Football.

The Tony Kornheiser Show is on the air daily M-F from 10:00 AM to Noon on Washington DC radio station WTEM (980 kHz AM) and streamed live on the station's website, ESPN980.com. It is also available as a podcast.

The Tony Kornheiser Co-Hosts are; Gary Braun, Jeanne McManus and (Marc) Nigel Sterne with news & weather from Kevin. Regular guests are; John Feinstein, David Aldridge, Bob Ryan, Liz Clarke, Mark Maske, Sam Smith, Sally Jenkins, Barry Svrluga, Lisa DeMoraes, Chuck Todd and of course his PTI Partner in Crime- Michael Wilbon.

He appeared on a local weekly Washington Redskins TV show during the NFL football season on Washington's Channel 50 in the early 1980s with Pete Wysocki, a popular former Redskins LB and local hero, which was televised from a local restaurant/bar in Washington, D.C. called "Champions".

He appeared on ESPN's The Sports Reporters beginning in 1988. He sometimes guest-hosted the program when the then-host of the show, the late Dick Schaap, was away.

He was also a panelist on Full Court Press hosted by George Michael on WRC-TV in Washington, D.C. during the NFL off-season until that show was canceled in December 2008 due to budget cuts. He sometimes guest-hosted Redskins Report on WRC when Michael was away.

He has appeared on numerous other ESPN productions, including SportsCenter, Who's Number One?, and multiple player's/sportsman's profiles entitled SportsCentury.

Pardon the Interruption

His lively segments with colleague Michael Wilbon on the radio and on Full Court Press, which mirrored their actual discussions in the newsroom of The Washington Post, sparked the idea for Pardon the Interruption well before the end of his run at ESPN Radio. As of August 2006, Pardon the Interruption is the highest rated sports talk show on ESPN.

Monday Night Football

When Monday Night Football moved from ABC to ESPN, Kornheiser received and accepted an offer to be a color analyst on Monday Night Football in early 2006. He was originally passed over in favor of Sunday Night Football commentator Joe Theismann; however, when play-by-play man Al Michaels left ABC to call Sunday Night Football for NBC, Kornheiser was brought in alongside Theismann and new play-by-play announcer Mike Tirico.

Unlike Wilbon, Kornheiser does most episodes of PTI in-studio due to his self-admitted fear of flying. Prior to joining MNF, his last trips outside of the studio were to cover Super Bowl XXXVI in New Orleans and to attend the NFL owners meetings in Orlando in 2006; Kornheiser both times traveled via train, though returned from the Orlando trip via airplane. On the April 6, 2006, edition of PTI, he expressed his dismay at the amount of travel required for MNF. Though he has mentioned on his radio program that he is taking steps to overcome his aviophobia, he in fact spent a five-week period on the road traveling to mainly western MNF sites, doing PTI via satellite.

Kornheiser returned for a second season of Monday Night Football. On January 9, 2007, Kornheiser told Newsday, "If they would like to have me back, my inclination is that I would like to do it again."

Kornheiser reportedly earned $1.8 million for being a Monday Night Football announcer and $900,000 for co-hosting PTI.

On May 18, 2009, ESPN announced that Kornheiser would be leaving Monday Night Football due to fear of flying. Former Oakland Raiders and Tampa Bay Buccaneers head coach Jon Gruden has replaced Kornheiser in the MNF booth.

The 2004—2005 sitcom Listen Up!, which aired on CBS, was loosely based on Kornheiser's life. It featured Jason Alexander as Tony Kleinman, and the sitcom's material mostly came from Kornheiser's columns (collected in I'm Back for More Cash) that he contributed to the "Style" section of the Washington Post; the columns took a humorous view of his family life.

While earning a name as a critic of many people and organizations, he has appeared sensitive to criticism directed toward his own work. Stephen Rodrick wrote for Slate that Kornheiser was allowed by ESPN to argue aimlessly on television and that his Washington Post column was being used to plug side projects rather than gather news from cited sources. Kornheiser called on Slate, then owned by the Post, to fire Rodrick.

After Kornheiser's first game on Monday Night Football, Paul Farhi wrote in The Washington Post that Kornheiser had emphasized the obvious, played third fiddle, and was reminiscent of Dennis Miller "in a bad way." Kornheiser responded during an interview on The Dan Patrick Show on August 15, 2006, saying that Farhi was a "two-bit weasel slug" and his own newspaper had back-stabbed him. His response generated more criticism from The Washington Post and other media outlets. Other criticism has come from Toronto Argonauts play-by-play commentator Mike Hogan, who said, "The thing that really bothers me is that Kornheiser doesn't seem to know his place. If you're there for comic relief, that's one thing. But for God's sake, leave the football analysis to guys who actually played the game." Former NFL offensive lineman Mike Schad also criticized Kornheiser, saying that "when people watch a game, they want to learn something. I don't need a guy who's sarcastic or trying to be funny. I love listening to Ron Jaworski on Monday Nights. He played the game and has lots of good insight and Kornheiser just gets in his way."

Mike Golic, an ESPN colleague of Kornheiser's, who had expressed skepticism regarding his prospects as an on-air analyst because he was never an athlete, said that his performance on MNF was "fine." Kornheiser's response was, "I just want to wring Golic's neck and hang him up over the back of a shower rod like a duck."

During a Monday Night Football telecast on September 15, 2008, Kornheiser made a comment about a clip of the ESPN Deportes crew's call of a Felix Jones touchdown, saying, “I took high-school Spanish, and that either means ‘nobody is going to touch him’ or ‘could you pick up my dry cleaning in the morning.’” Later in the broadcast, Kornheiser apologized on-air for the remark.

On February 23, 2010 various news sources reported that Kornheiser had been suspended from ESPN for two weeks for comments he made on his radio show about fellow high-profile ESPN personality Hannah Storm's wardrobe that day.

Hannah Storm in a horrifying, horrifying outfit today. She's got on red go-go boots and a catholic school plaid skirt. Way too short for somebody in her 40s or maybe early 50s by now. And she's got on her typically very, very tight shirt. So she looks like she's got sausage casing wrapping around her upper body. I mean, I know she's very good, and I'm not supposed to be critical of ESPN people, so I won't ... But, Hannah Storm, come on now! Stop! What are you doing? ... [She's] what I would call a Holden Caulfield fantasy at this point.

—Tony Kornheiser

In March 2010, Kornheiser commented: "The last time I looked, the roads were made for automobiles...We're going to be dominated as if this was Beijing by hundreds of thousands of bicyclists...They all wear my God with the little water bottle in the back and the stupid hats and their shiny shorts. They are the same disgusting poseurs that in the middle of a snowstorm come out with cross-country skiing on your block. Run 'em down...Let them use the right, I’m okay with that. I don’t take my car and ride on the sidewalk because I understand that’s not for my car Why do these people think that these roads were built for bicycles? ... They dare you to run them down.” Cyclist Lance Armstrong replied "Disgusting, ignorant, foolish. What a complete f-ing idiot." Kornheiser later apologized to Armstrong on-air and offered to go on a bike ride with him.

A meme featuring Tony Kornheiser's face and the word "Why" became popular on 4chan in late 2009.