Backman, 45, signed a two-year contract.
"We all feel very fortunate to have had a managerial candidate like Wally already in our organization," General Manager Joe Garagiola Jr. said. "Wally possesses the qualities that we believe will help return our organization to the success we have experienced in the past."
The 45-year-old Backman replaces Al Pedrique, who had been interim manager since Bob Brenly was fired in July.
Backman, a member of the New York Mets World Series championship team in 1986, has been a minor league manager the past eight years. He was at Class A Lancaster in the Arizona system this year.
The Diamondbacks had their worst season in 2004, ending with a record of 51-111.