Harman, who described Newsweek as "a national treasure", purchased the business from the Washington Post Company, which put it up for sale in May 2010, after failing to stem a steady stream of heavy losses.
"Harman has pledged not only to continue to produce a lively, compelling and first-rate news magazine, but also an equally dynamic Newsweek.com. He intends to keep a majority of Newsweek's very talented staff," said Donald Graham, chief executive of the Washington Post Company.
The deal ends almost a half-century of ownership by the Washington Post Company, which bought Newsweek in 1961. The magazine was founded Feb 17, 1933.
Sidney Harman is the founder of Harman International, a Connecticut-based manufacturer of speakers, stereos and in-car audio systems.