Blair was born in Columbia, Maryland, the son of a federal executive and a school teacher. He attended the University of Maryland, College Park, and was a student journalist during his time there.

Blair became editor-in-chief of its student newspaper, The Diamondback, for the 1996—97 school year. According to a letter later signed by 30 staffers, Blair made four serious errors as a reporter and editor that brought his integrity into question. The letter-signers alleged that questions about those errors were ignored by the board that owned the paper. Among the mistakes, they cited an award-winning story about a student who died of a cocaine overdose, who was subsequently found to have actually died of a heart ailment.

After a summer interning at The New York Times in 1998, Blair was offered an extended internship. He indicated that he had to complete some coursework in order to graduate, and The New York Times agreed to defer it. He returned to The New York Times in January 1999, when "everyone assumed he had graduated. He had not; college officials say he has more than a year of course work to complete." That November, he became an "intermediate reporter."

On April 28, 2003, Blair received a call from Times national editor Jim Roberts, asking him about similarities between a story he had written two days earlier and one written by San Antonio Express-News reporter Macarena Hernandez on April 18. Hernandez had a summer internship at The Times years earlier, and had worked alongside Blair. The senior editor of the San Antonio Express-News contacted The Times about close similarities between Blair's article and a story penned by their reporter Hernandez.

A small sample of the suspect articles:

• In the April 19, 2003 piece "In Military Wards, Questions and Fears From the Wounded", Blair described interviewing four injured soldiers in a naval hospital. He never went to the hospital and only spoke to one soldier on the phone, to whom he later attributed made-up quotes. Blair wrote that the soldier "will most likely limp the rest of his life and need to use a cane," which was untrue. He said another soldier had lost his right leg when it had only been amputated below the knee. He described two soldiers as being in the hospital at the same time, when in fact they were admitted five days apart.

• In the April 7, 2003 piece "For One Pastor, the War Hits Home", Blair wrote of a church service in Cleveland and an interview with the minister. Blair never went to Cleveland; he only spoke to the minister on the phone, then copied most of the article from an earlier Washington Post article. He also plagiarized quotations from the Cleveland Plain Dealer and New York Daily News. He fabricated a detail about the minister keeping a picture of his son inside his Bible, and got the name of the church wrong.

• In the April 3, 2003 piece "Rescue in Iraq and a ‘Big Stir' in West Virginia", Blair claimed to have covered the Jessica Lynch story from her home town of Palestine, West Virginia. Blair never traveled to Palestine, and his entire contribution to the story consisted of rearranged details from Associated Press stories.

• In the March 27, 2003 piece "Relatives of Missing Soldiers Dread Hearing Worse News", Blair again pretended to be in West Virginia, and plagiarized quotations from an Associated Press article. He claimed to have spoken to one relative who had no recollection of meeting Blair; said "tobacco fields and cattle pastures" were visible from Lynch's parents' house when they were not; erroneously stated that Lynch's brother was in the National Guard; misspelled Lynch's mother's name; and fabricated a dream that he claimed she had had.

• In the March 3, 2003 piece "Making Sniper Suspect Talk Puts Detective in Spotlight", Blair claimed to be in Fairfax, Virginia. He described a videotape of Lee Malvo, the younger defendant in the case, being questioned by police and quoted officials' review of the tape. No such tape existed. Blair also claimed a detective noticed blood on a man's jeans leading to a confession, which did not occur.

• In the February 10, 2003 piece "Peace and Answers Eluding Victims of the Sniper Attacks", Blair claimed to be in Washington, plagiarized quotations from a Washington Post story and fabricated quotations from a person he had not interviewed. Blair ascribed a wide range of facts to a man featured in the article, almost all of which the man in question denied. Blair also published information that he had promised was off the record.

• In the October 30, 2002 piece "US Sniper Case Seen as a Barrier to a Confession", Blair wrote that a dispute between police authorities had ruined the interrogation of suspect John Muhammad, and that Muhammad was about to confess, quoting unnamed officials. This was swiftly denied by everyone involved. Blair also named certain lawyers, who were not present, as having witnessed the interrogation.

The Times reported on Blair's journalistic misdeeds in an unprecedented 7,239-word front-page story on May 11, 2003, headlined "Times Reporter Who Resigned Leaves Long Trail of Deception." The story called the affair "a low point in the 152-year history of the newspaper."

The investigation saw heated debate over affirmative action hiring. Landman told the Siegal committee he felt being black played a large part in Blair's initial promotion to full-time staffer. "I think race was the decisive factor in his promotion," he said. "I thought then and I think now that it was the wrong decision."On May 14, 2003, while he was still Times executive editor, Howell Raines (who is white) acknowledged at a massive meeting of Times news staffers, managers, and its publisher, Arthur Sulzberger Jr., that Blair had gotten the breaks he had enjoyed because of his race. Five days later, Times op-ed columnist Bob Herbert asserted in his column that race had nothing to do with the Blair case: "Listen up: the race issue in this case is as bogus as some of Jayson Blair's reporting."

After resigning from The Times, Blair returned to college and said he planned to go into human resources. He is now a life coach in northern Virginia.