Curry, 28, scored his biggest professional contract, completing an impressive climb from an undrafted player out of Duke.
Curry was the third-rated 3-point shooter (45%) in the NBA for the Blazers last season. He actually finished ahead of his older brother, Steph, who shot 43.7%.
This will be Curry's second stint with the Mavericks. He played in 70 games for Dallas during the 2016-17 season, averaging nearly 13 points per game.
Curry also has spent time with the Grizzlies, Cavaliers, Suns and Kings.
Dallas also agreed to a four-year, $33 million deal with restricted free-agent power forward/center Maxi Kleber, sources told ESPN's Tim MacMahon.
The deal includes a team option for the final season.
Kleber, 27, averaged 6.8 points, 4.6 rebounds and 1.1 blocks in 21.2 minutes per game last season. He is expected to back up Kristaps Porzingis at power forward and see some spot minutes at center.
The agreement with Kleber does not impact the Mavs' salary-cap space because he is a restricted free agent currently on Dallas' books for a $1.8 million cap hold. The Mavs still have approximately $22 million in cap space with shooting guard Danny Green as one of their prime targets.
Veteran guard J.J. Barea is a lock to stay in Dallas on a one-year deal, according to sources, but the terms have not been determined.
Sources said that Barea, a longtime fan and locker room favorite who is progressing well in his recovery from a ruptured Achilles tendon, is willing to sign for the veteran's minimum but could get more money if the Mavs have cap space remaining after their other moves.