Willis led the Raptors in rebounding last year with an average of 8.3 per game, He also averaged 12 points per game.
During the 1998-99 season, Willis became only the 17th player in NBA history to pass 15,000 points and 10,000 rebounds.
Willis enters the final year of his contract this season in which he will be paid $2.6 million.
"I have family and things that I have to look toward," Willis told the Toronto Star on Thursday. "This is just a step in that right direction."
Willis, 37, came to the Raptors in a trade with the Houston Rockets in June of 1998.
The 14-year veteran has played in 1,062 career games with Atlanta, Miami, Golden State, Houston and Toronto.
He ranks eighth in the NBA with 3,498 offensive rebounds.
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