Following their championship-winning 2010–2011 season, the Mavericks entered the offseason with six free agents; only one of those six players returned to play with the team in 2011–2012. Starting center Tyson Chandler was traded to the New York Knicks in a three-team sign-and-trade deal; the Mavericks received guard Andy Rautins in return and waived him shortly thereafter. Forward Caron Butler signed a three-year deal worth $24 million with the Los Angeles Clippers. On December 14, reserve guard José Juan Barea announced that he would join the Minnesota Timberwolves. On December 19, reserve forward Peja Stojaković announced his retirement. Guard DeShawn Stevenson signed a one-year deal with New Jersey. Backup forward Brian Cardinal re-signed with the Mavs.
On Christmas Day the Mavs opened the 2011–12 campaign by playing in a finals rematch against the Miami Heat. The Heat were not out on the floor when the Mavs raised their banner, but came out of the gates impressive. They were up by 15 after the first quarter and 21 when the game went into halftime. During the third and fourth quarter the lead blew to 35 at most before the Mavs looked to start a heroic comeback. They cut the lead down to 11 at the end of the game but had chances to slice it down even more. Terry was the leading scorer with 23 points, but the Mavericks had 17 turnovers and allowed 15 offensive rebounds, which were two reasons the Mavs lost the opener.Lamar Odom got ejected for arguing about a call with the officials. In the second game of the season, against Denver, Delonte West started instead of Vince Carter. Denver went on a 20–0 run in the second quarter, ending the first half leading 69–42 and the lead blew to 31 in the third quarter. Sean Williams made his debut for the Mavs in the fourth quarter and scored 12 points on 4/4 shooting. Denver won the game by 22, 115–93 in the end. The Mavericks fell to 0–3 after a 102–104 loss to Oklahoma City where Carter gave the Mavs a one-point lead with 1.4 seconds to go before Kevin Durant hits a Buzzer beater three to put the Thunder at top. The Thunder improved to a perfect 4–0 record, their best start in franchise history. Dirk Nowitzki recorded his first double-double of the season with 29 points and 10 rebounds. For the first time this season, the Mavs took a lead into halftime against the Toronto Raptors. After the Raptors took the lead back and led by as much as seven, 68–61, the Mavericks answered with a 12–0 run and never looked back and won the game 99–86 to get their first win of the season.Ian Mahinmi scored a career-high 19 points and was the leading scorer for the Mavs. Nowitzki scored his 1,000th point against the Minnesota Timberwolves in a loss 82–99 and the Mavs fell to a 1–4 start. The Mavs handed the Thunder their first loss of the season with a 100–87 win. The Mavericks improved to 3–4 in a 98–89 win over Phoenix, in which Nowitzki played in his 1,000th game. After facing the San Antonio Spurs the Mavs fell to 3–5 in a 22-point blowout loss after just scoring 71 points. The Spurs hit eleven threes in the first half and were up by 26 at halftime. With Jason Kidd being out with a lower back injury and Carter to start at the shooting guard position the Mavs defeated the New Orleans Hornets 96–81 to improve to 4–5, though Nowitzki just went 2 of 11 from the field, he still was one of six player to score in double digits for the Mavericks. Nowitzki bounced back with a 9 of 10 shooting night with a +/– of +40 in a 100–86 win at Detroit to help the Mavs improve to a .500 record for the first time this season. West added 10 assists and five steals in absence of Kidd. After a 90–85 win at Boston the Mavs were a +.500 team for the first time this season. Rick Carlisle was ejected early in the second half after a non-call on Kevin Garnett after he grabbed Nowitzki on a play, he ran onto the court, across halfcourt and got two technical fouls. After Paul Pierce tied the game at 85 with 25 seconds to go, Nowitzki got the ball with ten seconds left and Garnett all over him. He would blow by him, get fouled by Brandon Bass but still managed to get the and-1. The Celtics called a timeout but the pass from Rajon Rondo to Ray Allen was fumbled and went out of bounds and the Mavs were able to hold on to the win. Nowitzki scored his 23,000th point of his career against Milwaukee in a 102–76 win to improve to a 7–5 record and the Mavs captured their fourth win in a row. With Kidd back in the lineup, the Mavericks won their fifth straight game by blewing out the Sacramento Kings 99–60. After five wins, the Mavs received a close loss at the Lakers after Derek Fisher hit a game winning three-pointer with 3.1 seconds to go.Vince Carter injured his left foot by taking the last shot to try and tie the game. Without Carter, the Mavs took on the Los Angeles Clippers and lost their third game on a late game three-pointer, this time by Chauncey Billups with 1 second to go after Terry got the Mavs ahead 89–88 with two three-pointers. After that loss the Mavs took on Utah and got away with a 94–91 win, Shawn Marion scored 22 points and Rodrigue Beaubois scored 17 to help them to improve to a 9–7 record. Without Nowitzki, who sits out with a sore right knee, the Mavs won at New Orleans 83–81 for the first time since 2007. Phoenix came to town and the Mavericks were able to win 93–87 behind 29 points from Marion. The Mavs lost to the T-Wolves the day they got their 2011 NBA Champion rings by fifteen points. Against Utah, Carter returned to the lineup, but West was out due to a hamstring injury, the Mavericks won behind 22 points from Beaubois who got his first start of the season. Kidd injured himself during the first quarter and did not return due to a strain calf injury. With Nowitzki back in the lineup, the Mavs won against their rival San Antonio 101–100 after Overtime.Jason Terry scored a team- and season-high 34 points. The Mavs went on the road to Phoenix to win in blowout fashion 122–99 with West and Carter hitting 10 of their 13 tries from behind the arc. Without Lamar Odom, Brendan Haywood and Kidd the Mavericks lost to the Thunder 86–95. Marion injured his knee in the second quarter but returned to the game, coach Carlisle was ejected for kicking the ball into the stands. Against Indiana the Mavericks fell short and lost by 11 to drop to 14 and 10. Nowitzki scored 30 points, Paul George hit 7 of his 11 tries from downtown and scored his career-high 30 points. The Mavericks lost their third game in a row at Cleveland 88–91 when Terry missed the shot to tie it. Without Kidd again, the Mavs were able to win at Denver, with Nowitzki going for 25 and 9 while Carter added 8 assists. In the last season matchup against Minnesota, Nowitzki scored 33 points while Kidd was making his comeback to help the Mavs to push their record to 16 and 11. Against Portland the Mavs needed two overtimes periods to get the win. Nowitzki twice had the chance to put the game away but missed both times, before he hit a shot in the second overtime to ice the game. When the Clippers came to town, Caron Butler got his ring but the Mavs the win. Butler missed the chance to take the lead with a three and the Mavs won by four. Without Terry and Beaubois the Mavs defeated the Nuggets in blowout fashion. West went out with a dislocated finger. Without Terry, Beaubois and West the Mavs took on Philadelphia and won after being down by 14 at the half, before Nowitzki scored 24 points in the second half, just as much as the Sixers. The Mavericks traveled to New York City to take on the Knicks and their new sensation Jeremy Lin. Terry was back in the lineup, but the Mavs lost by seven in the end after being up 10 in the third quarter, while Nowitzki put up a new season-high 34 points. In a win against the Celtics, Nowtzki recorded his 1000 block of his career and moved up to No. 20 on the all-time scoring list. At the last game before the All-Star break the Mavs lost to the Lakers. After the All-Star break the Mavs took on the New Jersey Nets and lost by one, when Jason Kidd missed a buzzer-beating three-point attempt.Brook Lopez scored 38 points for the Nets. On the next night, at Memphis the Mavs failed short with Nowitzki playing just nine minutes before going to the locker room with a tight back. Mavs lost their fourth straight game at New Orleans. After four consecutive losses the Mavs beat the Jazz by 6, with Nowitzki going off for 40 points. The Mavericks lost Haywood in the opening play at Oklahoma and lost the game by four while shooting 23 less free throws. On the following day, the Mavs won against the Knicks after blowing a 19-point lead before Nowitzki took over in the fourth quarter. On the first night of their back-to-back-to-back they lost to the Suns by two. On the next night, the Kings won against the Mavs' who dropped to the seventh place in the conference. The Mavericks ended their only three games in three nights stint with another loss, this time getting blown out by Golden State. Back home and after two days of rest, the Mavs' defeated Washington by nine. Two days later they took on Charlotte and won by 5 despite being up by a higher margin. Without Marion, who missed his first game of the season, the Mavericks beat the Spurs by seven. At Denver, the Mavericks won by 17 in blowout fashion. Without Haywood, Marion and West the Mavs lost to the Lakers. With Marion back in the lineup but withput Odom due to a DNP-CD, the Mavs lost at the Spurs by 17. On the next day, at Houston the Mavs won after overtime 101–99. When Hoston came to visit the Mavs, the Mavericks won by 9 after giving just up 51 points in the last three quarters. In the second meeting against the Heat the Mavs got blown out by 21. They completed their Florida road trip by winning at Orlando, with Nowitzki hitting the go-ahead bucket with 5.9 second to go. Hedo Türkoğlu missing the buzzer beating three-point attempt and Ryan Anderson failed to convert the putback layup. Without Kidd and Odom, injured and ill, the Mavs got beaten badly by the Clippers. Against Memphis, the Mavs got back on the winning track by beating them by 10. Against the Blazers the Mavs lost in Overtime, despite being up by as much as 15. A day later, at Memphis the Mavs lost by 5, while being down by 19 after the first quarter. After the departure of Odom, the Mavs took on the Kings and won by 10. At Golden State they won by nine after being up by as much as 19. With Kidd getting a rest, the Mavs won at Portland 97–94 despite being up by more than 20. Against the Lakers the Mavs lost in overtime, although some questionable calls were made in the favour of LA. After triple overtime they failed to the Jazz 121–123. Against the Rockets they trailed by 6 going into 4th quarter, in a crucial game for a playoff berth with predecisive character. They cancelled out the deficit and went on to win 117–110 with Nowitzki shooting 21 of his 31 2nd-half points (35 in total) in the last quarter. This marked their 4th last quarter comeback for the season. The playoff spot was guaranteed the next day, without playing themselves, because of the loss of the Rockets to the Hornets. They won their last home game of the regular season 104–94 against Golden State the next day. Without either Kidd or Terry, the Mavs took on Chicago but fell short and lost by ten. After four days, with Kidd still resting, they lost 89–106 at Atlanta to close out the regular season. They clinched the seventh spot to play the Thunder in the first round of the playoffs, which also happened to be a rematch of the conference finals from the year before. The series was about to start just two days after the last regular-season game.
The Mavericks opened their series against Oklahoma City Thunder on the first day of the playoffs. The game was close throughout and the Mavs took the lead by seven with 2 minutes to go. Dirk Nowitzki turned the ball over several times in the crucial stretch and the team stayed scoreless on four straight possessions. With nine seconds to go, the Mavs had a one-point lead, when Kevin Durant hit a shot that bounced a couple of times on the rim and backboard and fell through with 1.5 seconds to go. Shawn Marion's attempt for a half court shot came too late and the Thunder took Game 1. Game 2 was closeout again, even though the Mavs were down by 16 in the first half. They came back and took the lead in the third quarter. The fourth quarter was much of a freethrow contest, James Harden made all of his late in the game and both, Nowitzki and Jason Terry missed his threes. Terry had two tries to send it to overtime, but missed. Thunder were up 2–0. The Thunder took a commanding 3–0 lead after their blowout win in Game 3. Despite having a 13-point lead going into the fourth quarter the Mavs lost by six in Game 4 and were swept.