Adrian Wojnarowski of ESPN.com previously reported the deal is for two years and $12 million.
Mack averaged 7.8 points and 2.8 assists per game in 55 contests, including nine starts, last season for the Utah Jazz.
While his playing time fluctuated, he showed plenty of ability when he was on the court. In four playoff losses to the Golden State Warriors, Mack averaged 12.3 points, 4.8 rebounds and 3.8 assists in 28.2 minutes per contest.
This will be Mack's fifth team since he was drafted in the second round in 2011. After beginning his career with the Washington Wizards, he had a short stint with the Philadelphia 76ers before latching on with the Atlanta Hawks. He became a valued contributor for that team, appearing in the playoffs in three different seasons, before being traded to the Jazz.
He closed the 2015-16 season with 27 straight starts for Utah, averaging 12.6 points, 3.8 rebounds and 5.3 assists per game.
In Orlando, Mack will likely provide depth behind the inconsistent Elfrid Payton.
And though this move won't turn the Magic into contenders, it should help the young squad compete in what has become a wide-open Eastern Conference.