Lee, a veteran power forward who cleared waivers after receiving a buyout from the Boston Celtics, agreed to sign for the prorated portion of the Mavs' $2.1 million cap-room exception and arrived in Dallas on Sunday.
"We think he can play both big positions, some 4 and some backup 5," coach Rick Carlisle said. "I just think he's a quality veteran player who has been in a situation in Boston where they were overstocked and decided to go with some younger guys. We believe he can help us."
Lee, 32, is a two-time All-Star with career averages of 14.4 points and 9.2 rebounds per game.
However, he fell out of the rotations for the Golden State Warriors and Celtics the last two seasons. He averaged 7.1 points and 4.3 rebounds in 15.7 minutes per game in his 30 appearances for Boston and hoped to find a bigger role on a playoff team after receiving his buyout.
"He's a smart player," Mavs star Dirk Nowitzki said. "He knows how to play. He can score around the basket, he's a good passer out of the post, he's a good rebounder, which sometimes we have issues with our rebounding, so he should help us there. I just think it's another solid veteran that wants to win."
The Mavs waived reserve guard John Jenkins to create a roster spot for Lee.