Pioli was director of player personnel for the New England Patriots from 2000-08, including six seasons with Dimitroff, who directed college scouting. He was the Kansas City Chiefs' general manager for four years before leaving by mutual agreement in January 2013.
Pioli, 48, will join the Falcons on Feb. 3, after he completes his contract with NBC Sports and SiriusXM Radio.
Pioli began his NFL career in 1992, when he was hired by Bill Belichick as a scouting assistant for the Cleveland Browns. Pioli was made the New York Jets' director of pro personnel in 1997 before joining Belichick in New England.
Falcons owner Arthur Blank said Dimitroff initiated the push to bring in Pioli.
"This move was made as a result of Thomas' competitive drive to build the best personnel team in the NFL, and the addition of Scott to his team certainly reflects that," Blank said.
Dimitroff said Pioli is "one of the most respected and adept talent evaluators in the NFL."
"We have worked together well in the past and been friends for more than 20 years," Dimitroff said. "We have had the opportunity to experience a lot of success together, and I am very pleased that he has agreed to join our personnel team so we can work together again."
The Falcons were 4-12 in 2013 after five straight winning seasons.
"We have made the commitment to improve every aspect of our organization this offseason, and with the addition of Scott to our personnel department, we have taken an important step to enhance our scouting staff," Dimitroff said.
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