"I knew," Batum said. "I knew he was going to make it."
Aldridge finished with 29 points and 13 rebounds for Portland, which trailed 101-94 with 2:18 left. J.J. Hickson had a season-high 26 points and 15 rebounds for his 25th double-double.
After Wesley Matthews made two free throws to pull the Blazers to 101-98 with 52 seconds to go, Batum's 3-pointer tied the score.
Dirk Nowitzki answered with his own 3 before Aldridge also had a 3 -- the first one he has made this season -- to tie it at 104 with 4.9 seconds left. O.J. Mayo was called for charging with 1.5 seconds to go, and Aldridge hit his jumper after the inbounds pass from Matthews with 0.2 seconds left for the victory.
"He (Batum) has his hand up. He said he had a lot of faith in me," said Aldridge, recently named an All-Star reserve for the second straight year. "I had to watch it go in."
As the confetti streamed down from the rafters of the Rose Garden, Aldridge was tackled by his teammates.
"He was smiling like a rookie, like his first NBA game," Batum said about Aldridge afterward. "We needed those two shots (the 3-pointer and the game winner). They show people that he really is an All-Star. He is an All-Star. He's a go-to guy."
Nowitzki finished with 26 points for Dallas, which had won six of its past eight games.
"We cannot let Aldridge get set on the block 10 feet from the basket and let him turn around and shoot a wide-open shot," Nowitzki said. "We make those mistakes, especially on the road, and you are going to get bit."
The Mavericks were without center Chris Kaman, who sustained a concussion in a collision during practice Monday, according to coach Rick Carlisle. There was no timetable for Kaman's return. He is averaging 12.4 points and 6.2 rebounds per game this season.
The injury comes as the Mavericks have juggled their centers, starting a different one in each of their past three games. Kaman, Elton Brand and rookie Bernard James have each taken turns. Brandan Wright also plays at center for the Mavs.
James made his second straight start against the Blazers.
"It helps to have depth," Carlisle said. "We need all those guys but this (Kaman's injury) is a big hit for us."
In a first half marked by lackluster defense on both sides, Nowitzki's long jumper put Dallas up 37-28.
Nowitzki, who missed the Mavericks' first 27 games after surgery on his right knee, hit another jumper that extended the lead to 47-36. Darren Collison scored 10 straight points, and Dallas closed out the first half with a 19-6 run to take a 59-42 lead.
Portland struggled with its 3-point shot, going 2-for-12 in the first half.
Mayo's step-back jumper pushed Dallas' lead to 69-48 after the break.
Batum, who had two triple-doubles last week for the Blazers, didn't hit from the field until a 3 with 4:43 left in the third quarter that made it 74-58. Luke Babbitt hit a 3-pointer and Aldridge made a short jumper to narrow it, and Portland pulled closer to 78-72 after Aldridge and rookie Damian Lillard each hit free throws.
Portland finished the third on a 16-4 run to get within 74-80 to start the final period.
"This type of loss is about as tough as it gets in the league," Nowitzki said. "We played well enough to win it. Tonight we found a way to lose, instead of finding a way to win. That's the sad thing."
The Mavs beat the Blazers 114-91 on Nov. 5 in Dallas. ... The Mavericks were flagged with a technical for six players on the floor late in the first half. ... Portland had 38 points in the third quarter, a season high. ... Aldridge and Hickson are the first Blazers to have at least 26 points and 13 rebounds in the same game since Clyde Drexler and Jerome Kersey on Dec. 2, 1987, against the Lakers. ... It was the 10th time this season the Blazers won a game in which they trailed at halftime. ... Before Tuesday night, Aldridge had gone 0-for-9 from 3-point range.