The team did not announce terms of the contract. But a basketball official, speaking Thursday on condition of anonymity because the deal had not yet been signed, told The Associated Press that the four-year contract extension is worth $20 million.
Detroit drafted Maxiell, 25, with the 26th overall pick in 2005.
The 6-foot-7, 260-pound forward is one of the Pistons' top reserves and likely will have a larger role in the years to come. He had career highs last season, averaging 7.9 points, 5.3 rebounds and 1.2 blocks in 82 games.