The 43-year-old Pioli will be introduced on Wednesday as Chiefs general manager, replacing Carl Peterson. Pioli was seen packing up his office Tuesday afternoon, a Patriots source told ESPN's Michael Smith.
"He will have complete charge of football operations," Ryan Petkoff, a spokesman for Chiefs chairman Clark Hunt, told The Associated Press. "He will report only to Clark."
The decision to hire Pioli likely means Herm Edwards will not be back as Chiefs head coach next season. Among the top candidates to succeed Edwards is New York Giants defensive coordinator Steve Spagnuolo.
A source close to the situation told ESPN.com's Bill Williamson that Edwards sent his assistant coaching staff home to await word on the future in light of the Pioli hiring news.
The Kansas City Star reported that according to two coaches, Edwards and the staff could be dismissed as soon as Wednesday.
Pioli, who became vice president of player personnel for the Patriots in 2002 and spent nine years working with head coach Bill Belichick, also interviewed for the general manager vacancy in Cleveland.
He inherits a young team coming off a 2-14 season but is stepping into a situation that seems ripe for a quick turnaround.
The fan base is loyal, though restive, and the team will be playing next year in a virtually new stadium. Arrowhead, which opened in 1972 and is notorious for being loud and rough on visiting teams, is undergoing a $325 million renovation, which includes new luxury boxes, wider concourses and enhanced amenities in addition to new practice facilities, an enlarged indoor field and a brand new state-of-the-art headquarters building.
In addition, the Chiefs are about $32 million under the salary cap, extra money that will come in handy because they own the overall No. 3 pick in the draft. Besides that, there are a number of promising young players who Edwards was counting on as the foundation of his rebuilding project.
Pioli will be handling the football side of the operations, with the Chiefs still to hire a president who would be in charge of the business end of things. According to the Star, the job is expected to go to longtime team executive vice president Denny Thum.
Pioli, the son-in-law of Miami Dolphins boss Bill Parcells, has been honored many times for his contributions to the Patriots' three Super Bowl championships. With Pioli working with Belichick, the Patriots used an effective mix and match of trades, free-agent signings and draft selections to dominate the league. In 2007, six players drafted by Pioli and Belichick made the Pro Bowl.
"We are very excited to welcome Scott to the Chiefs," Hunt said in a statement. "With his proven track record of success, Scott is the finest player personnel executive in the NFL, and we look forward to his leadership in building a championship organization."
Patriots owner Robert Kraft praised Pioli as an "integral part of the many championships the New England Patriots have celebrated this decade."
"Scott is a great evaluator of talent," Kraft said. "He is thorough in his evaluations, extremely organized and has done a tremendous job mining all possible resources to help coach Belichick and his staff field the players needed to win consistently. He has played an important role in building a championship tradition with players that I am proud to call Patriots."
Pioli's NFL career started when Belichick hired him as a pro personnel assistant for the Browns in 1992. Belichick then brought him to New England shortly after he became head coach of the Patriots.
From 2000 to 2008, the Patriots were an NFL-best 102-42 in the regular season and rang up 14 playoff wins.
"To sum up in words everything Scott Pioli has meant to this organization and to me personally would be difficult, if not impossible," Belichick said. "From the day I met him, he has demonstrated a passion for football and respect for the game that is second to none."
Patriots director of player personnel Nick Caserio will replace Pioli as vice president of player personnel, league sources told ESPN.
A club spokesman confirmed there had been no determination made on Edwards' status. That may have been a point of discussion between Pioli and Hunt when they negotiated their deal. Hunt signed off on the rebuilding project that Edwards launched this year and said in training camp he knew it would be a painful process early on.
And it certainly was. Beset by injury, including season-ending mishaps to the top two quarterbacks, the Chiefs beat only Oakland and Denver and set a number of team records for defensive futility. Their 10 sacks were an NFL-low since 1981, when that statistic started being recorded.
Yet, when he announced the resignation on Dec. 15 of president, CEO and general manager Peterson, Hunt said he thought Edwards was the best man for the Chiefs program going forward. But he also said the new general manager would have "significant input" into the final decision.
Edwards' first season in Kansas City was a hit. The Chiefs went 9-7 in 2006 and captured the last wild-card playoff spot. They were routed by Indianapolis, but Edwards was just the fifth man to take two different teams to the postseason in his first year; he also did it in 2001 with the Jets.
He wanted to begin dismantling an aging team and start rebuilding that next season but ran into opposition from a front office that believed there was enough left for another playoff run. But after an encouraging 4-3 start, age and ineffectiveness at several key positions began creating problems. The Chiefs ended 2007 on a nine-game losing streak. Then Hunt agreed it was time to tear it down and rebuild.
Now Pioli takes charge of those efforts.
Information from The Associated Press was used in this report.