The Magic made the announcement Monday.
"Having quality big men is an absolute must in our league, and Marcin has worked very hard to fit into that category," Magic general manager Otis Smith said in a statement. "He provides tremendous depth to our frontcourt and we're happy to bring him back."
Gortat's agent, Guy Zucker, said the center "was definitely very disappointed today." He said Gortat was back in his native Poland, where he'd already been telling everyone he was headed to the Mavericks.
In Orlando, Gortat will likely see spotty playing time behind Howard.
"It was definitely about the opportunity to find out how good he can really be," Zucker said. "We had requested that Orlando not match the offer. We stated the fact that he sincerely wanted the chance to carve his own path, be his own man, so to speak, which is not going to be realistically possible in Orlando."
Gortat averaged just 3.8 points and 4.5 rebounds per game last season and 3.3 points and 3.2 rebounds during the Magic's run to the NBA Finals, but his opportunities in Orlando were limited behind All-Star center Dwight Howard.
The 6-foot-11, 240-pound center made about $700,000 last season, his first full year in the NBA. He likely will remain in a backup center role or play sparingly alongside Howard at power forward.
But Gortat earned the big pay raise in large part because of some highlights in the Magic's playoff run.
Gortat filled in for Howard in the Game 6 clincher against Philadelphia in the opening round after Orlando's All-Star was suspended, adding a few powerful dunks that earned him the nickname the "Polish Hammer" from teammates. He also had a pair of blocks on Cleveland's LeBron James in the conference finals, and he saw his minutes increase in the Finals because of the size of the Los Angeles Lakers.
The decision is a bold and costly one for the Magic, who will plunge further into luxury-tax territory than many rivals anticipated after their recent trade for Vince Carter by first signing Brandon Bass away from Dallas to a four-year deal worth a reported $18 million and then matching on Gortat.
Retaining Gortat and adding Bass will likely take the Magic's payroll into the $80 million range for next season, which would force Orlando to cut a luxury-tax check of more than $10 million in July 2010 barring roster moves between now and June 30 of next year to lower that figure.
Information from ESPN.com's Marc Stein and The Associated Press was used in this report.