Weaver agreed to a four-year contract, sources tell ESPN.
"I'm excited for the challenge of building this team into a consistent winner and assembling the pieces to compete at a very high level," Weaver said in a statement announcing the hiring.
Weaver will become the ninth black GM in the league and work with senior adviser Ed Stefanski in running the Pistons' basketball operations.
With his strong history in player personnel decisions across a dozen years in Oklahoma City, Weaver had been a focus of a Detroit search that desperately needs to change its fortunes in the draft and bring young talent into the organization.
Weaver will be the fourth GM to rise out of the Thunder front office under Sam Presti in the past decade. Rich Cho, Rob Hennigan and Michael Winger are the others. Only the Spurs have had as many executives hired as general managers in that span.
Especially with Westbrook, few teams had him evaluated as high as the Thunder -- then the Sonics -- who were picking at No. 4 in 2008. Pistons chairman Arn Tellem was running Wasserman Media Group when Weaver identified and pushed for the drafting of Westbrook, a client of Wasserman agent Thad Foucher, in 2008.
Weaver started his basketball career as coach of the DC Assault AAU program before stops at three colleges -- Pittsburgh, New Mexico and Syracuse. He then joined the Utah Jazz in player personnel. Presti hired him before the Sonics move to Oklahoma City in 2008.