The Golden State Warriors became the first team in the Western Conference to clinch a play-off spot with a 110-88 win over the Oklahoma City Thunder.
The win means the Warriors – who cannot finish any worse than in eighth place – move into their seventh straight play-off berth.
The San Antonio Spurs extended their winning run to eight games as they overcame the Portland Trail Blazers 108-103.
DeMar DeRozan finished with 21 points for the Spurs but there was further disappointment for Portland after CJ McCollum exited the court in the third quarter with a leg injury.
In New Orleans, the Phoenix Suns edged the Pelicans 138-136 in a nail-biting finish at the Smoothie King Center.
Coach Alvin Gentry called for a timeout after Josh Jackson tied the game with a three-pointer in the dying seconds of overtime, but the Pelicans had used up all their timeout calls and were assessed a technical foul.
Devin Booker made sure to hit the free throw, leaving Phoenix to run with the lead from there and hand New Orleans their sixth loss in a row.
Tim Hardaway Jr top-scored for Dallas with 22 points and Dirk Nowitzki finished with 14.
Cleveland have now lost their last three games.
The Denver Nuggets strengthened their hold on a play-off spot with a 102-100 win against the Indiana Pacers, while Donovan Mitchell's 24 points helped Utah Jazz defeat the Brooklyn Nets 144-98.
Kyrie Irving finished just shy of a triple-double with 30 points, 11 rebounds and nine assists in the Boston Celtics' 129-120 victory over the Atlanta Hawks, and Bradley Beal scored 40 points as the Washington Wizards saw off the Memphis Grizzlies 135-128.