Dallas (2-10) led 64-53 at halftime and by as many as 16 points in the second half. After Washington closed to within 90-88 with 9:09 remaining, the Mavericks pushed back with a 15-5 run.
John Wall had 23 points and 14 assists for the Wizards (5-5) in his return to the lineup. Wall sat out Washington's 107-96 win at Toronto on Sunday after injuring his left shoulder Friday in a home loss to the Cleveland Cavaliers.
Bradley Beal also scored 23 points for the Wizards.
Washington only shot 42.7 percent from the field against one of the league's worst defenses and showed little resolve in its third consecutive home loss. The Wizards opened the season 3-0 but have lost five of seven.
Dallas hit 47.3 percent of its field-goal attempts.
Washington trailed 90-74 after Matthews sank a 3-pointer with 55 seconds remaining in the third quarter. The Wizards scored the next 14 points, capped by a four-point sequence as Dirk Nowitzki received a technical foul after Otto Porter converted a three-point play. Dallas scored the next five points and eventually led 104-91 with 4:19 left.
Dallas ranked 28th in scoring with 97.9 points per game, which made its first-half production surprising -- except to Washington observers. The Wizards surrendered 122 and 130 points in home losses last week to the Phoenix Suns and the Cavaliers.
The Mavericks entered Tuesday allowing opponents to sink 48 percent of their field-goal attempts while ranking 29th in hitting shots from the floor (42.0 percent).
Leading 36-34 after the first quarter, the Mavericks opened the second with a 9-0 run and eventually led 64-49. Barnes scored nine of 16 first-half points in the second quarter.
Playing with athletic tape on the injured shoulder, Wall had 19 points and nine assists in the first half.
Beal averaged 38 points in his previous three games.
NOTES: Dallas F Dorian Finney-Smith (left knee soreness) had five points in 16 minutes after sitting out the previous four games. ... Wizards G John Wall made all eight of his free-throw attempts in the first quarter and finished 13 of 18. Wall missed 11 of 16 in his two previous games, including a 5-of-12 performance on Friday, when he injured his left shoulder. ... Dallas is off until Saturday, when the Cleveland Cavaliers visit. ... The Wizards close out their season series with the Lakers on Thursday. Los Angeles won the first meeting 102-99 in overtime on Oct. 25 after Washington blew a double-digit lead in the fourth quarter.