The Blazers made a push in the fourth quarter, outscoring the Mavericks 34-28.
The Mavs did not repeat their mistakes from Game 4, however, and managed to hold on to their lead in Portland to close out the series in Game 6.
Dirk Nowitzki led all scorers with 33 points and 11 rebounds. Jason Terry added 22 points and 8 assists.
Gerald Wallace led Portland with 32 points and 12 rebounds.
The Mavericks won their second post-season series since falling to the Miami Heat in the 2006 NBA Finals. They will travel to Los Angeles to face the Lakers in the Western Conference semifinals with Game 1 on Monday night.