Stewart was born in Quincy, Illinois. A graduate of DePauw University and Harvard Law School, James B. Stewart is a member of the Bar of New York and Bloomberg Professor of Business and Economic Journalism at the Columbia University Graduate School of Journalism. He is a former associate at New York law firm Cravath, Swaine & Moore. In 1988, he won the Pulitzer Prize for Explanatory Journalism for his articles in The Wall Street Journal about the 1987 dramatic upheaval in the stock market and insider trading. These writings led to the publishing of his best-selling work of non-fiction called Den of Thieves that recounted the criminal conduct of Wall Street arbitrager Ivan Boesky and junk bond king, Michael Milken.

His 1999 work, Blind Eye: The Terrifying Story Of A Doctor Who Got Away With Murder, won the 2000 Edgar Award in the Best Fact Crime category. DisneyWar, his 2005 book on Michael Eisner's reign at Disney, won the Gerald Loeb Award for Best Business Book. In 2007 he was ranked 21st on Out magazine's "50 Most Powerful Gay Men and Women in America."

He is currently a contributor to The New Yorker and an Editor-at-Large for Smart Money magazine and SmartMoney.com. Stewart also serves on the board of trustees of his alma mater, DePauw University, and is past president of that board.