Cauley-Stein, 26, provides the Mavericks with a backup big man to replace Dwight Powell, who suffered a ruptured right Achilles tendonTuesday.
Dallas is sending the Utah Jazz's 2020 second-round pick to the Warriors in the deal.
After spending his first four seasons with the Kings, Cauley-Stein signed with the Warriors this offseason on a two-year deal. He's set to make $2.17 million this season and $2.28 million next, although he has a player option for Year 2.
In a separate deal, the Mavericks traded Isaiah Roby and cash to the Oklahoma City Thunder for Justin Patton. The Mavericks have requested waivers for Patton to open up a roster spot and are using the $11.7 million trade exception created from the Harrison Barnes trade last February to acquire Cauley-Stein.
The trade drops Golden State to $2.57 million below the hard cap and saves the Warriors $5.66 million toward the luxury tax.
The 7-foot Cauley-Stein, who missed all of training camp and the preseason games because of a left foot injury, is averaging 7.9 points, 6.2 rebounds, 1.5 assists and a team-leading 1.2 blocks in 41 games (37 starts) for the Warriors.
Woj: Mavs out of Drummond sweepstakes with Cauley-Stein trade
Adrian Wojnarowski says the Mavericks are most likely out on trading for Andre Drummond after acquiring Willie Cauley-Stein from the Warriors for a second-round pick.