Dallas acquired the rights to Emir Preldzic, a 2009 second-round draft pick, in exchange for Blair.
"DeJuan gives us a tough inside presence who can score and rebound at both frontcourt positions," Wizards president Ernie Grunfeld said in a statement released Wednesday. "His addition makes our bench even deeper and will allow us to be flexible with our lineups."
Blair posted a tweet referencing his new NBA home Wednesday afternoon.
- DeJuan Blair (@DeJuan45) July 16, 2014
ESPN.com reported Sunday that the Wizards and Mavericks were in advanced talks on a sign-and-trade deal that would land Blair alongside Paul Pierce and Kris Humphries as new additions to Washington's up-and-coming roster.
The Mavericks, sources say, promised Blair that they would try to sign-and-trade him to a new team to help him as much they could financially as a reward for contributions the bruising forward made last season, notably during Dallas' seven-game battle with the eventual champion San Antonio Spurs in the opening round.
Working on a minimum contract, Blair played with an intensity and tenacity that the Mavs sorely needed in their frontcourt. Due to Samuel Dalembert's inconsistency and Brandan Wright's matchup-based playing time, Mavs coach Rick Carlisle often went to Blair, 25, as the primary center off the bench.
In the San Antonio series, Blair's physical nature changed the dynamic of a first-round battle between old Texas rivals that proved to be the Spurs' toughest test on their championship run.
Blair was ejected late in a pivotal Game 4 against the Spurs when he kicked center Tiago Splitter in the head during a loose-ball foul. Blair later said it was an accident. Although the ensuing one-game suspension hurt the Mavs, Blair's efforts helped them push the Spurs -- who drafted Blair No. 37 overall in 2009 -- to a Game 7, which San Antonio won in a rout.
ESPNDallas.com's Bryan Gutierrez contributed to this report.