The person spoke on condition of anonymity Friday because no announcement had been made. The move sets the stage for the 6-foot-11 Monroe to become an unrestricted free agent after this season.
The 24-year-old Monroe has been a consistent scorer for the Pistons since they drafted him with the seventh pick in 2010, but his future with the team is in doubt after Detroit failed to sign the restricted free agent to a long-term contract this offseason.
Yahoo! Sports first reported the signing Friday.
Monroe averaged 15.2 points and 9.3 rebounds in 2013-14 -- numbers almost identical to what he posted during the previous two seasons. He's shot 51 percent from the field over the course of his career.
The Pistons would have had a chance to match any agreement he made with another team this offseason -- an advantage they would lose once Monroe becomes an unrestricted free agent.
The pressure will be on Detroit to return to the playoffs this season under new coach Stan Van Gundy. The Pistons still have Monroe, along with fellow frontcourt players Andre Drummond and Josh Smith.
Detroit has missed the playoffs the last five seasons and gone through several coaches in the process. Monroe and Drummond -- the team's two young big men -- have been among the few bright spots, but it's not clear how much longer the Pistons will be able to hold onto Monroe.