Mr. Middlebrook, 67, had been VP-global sales, service and marketing operations since September 2004 and helped GM expand worldwide.
His successor is Jonathan Browning, 48, currently VP-sales, marketing and aftersales for GM Europe, who starts June 1.
Mr. Browning's post will be taken June 1 by Brent Dewar, 53, currently VP-field sales, service and parts in North America. Mr. Dewar is in the process of reforming GM's U.S. regional dealer ad groups.
Steady rise up the ranks
Mr. Middlebrook joined GM's Oldsmobile division in 1959. The engineering graduate went on to get a master's degree in marketing and climbed the ranks at GM: He became Pontiac marketing director in 1977; VP-sales, service and marketing at Saturn Corp. in 1985; general manager of the Pontiac division in 1989; and general manager of Chevrolet in 1989.
During his stint running Pontiac as general manager, he was credited with initiating a brand-management system that was a guide for GM in the mid-1990s.
"John Middlebrook has made tremendous contributions to GM in a variety of roles over the past 49 years," Rick Wagoner, chairman-CEO of GM, said in a statement. "He is well known and highly respected and admired throughout the industry as a true sales and marketing professional. I've enjoyed working closely with John in the past several years as he has led GM's efforts to integrate and leverage our sales and marketing capabilities globally."