Barlett was raised in Johnstown, Pennsylvania. After attending Pennsylvania State University, he served three years as a special agent with the US Army Counter Intelligence Corps until 1956, when he began his journalistic career as a reporter for the Reading (Pennsylvania) Times. Nine years later he become an investigative journalist for The Cleveland Plain Dealer, and later took similar jobs with The Chicago Daily News and The Philadelphia Inquirer, where he was to join his collaborator Steele. In 1997, Barlett and Steele became an editors-at-large for Time.

In 1972, during one of their earliest collaborations for The Inquirer, Steele and Barlett pioneered the use of computers for the analysis of data on violent crimes. Their 1992 Inquirer series America: What Went Wrong? was named by the New York University School of Journalism as one of the 100 best pieces of journalism of the 20th century. Rewritten as a book it became a No. 1 New York Times bestseller. It is one of seven books Barlett and Steele have published.

Barlett and Steele have been hired by Vanity Fair to be contributing editors on the understanding that they would contribute two articles each year. They were available for this new assignment after Time determined that they had insufficient space for long journalistic investigations. In 2007, Barlett and Steele were featured in the PBS documentary series, America's Investigative Reports, in an episode entitled "Friends In High Places."

Barlett is married and has a son as well as a stepson.

"America: What Went Wrong?"

"America: Who Stole the Dream?"