The win guaranteed the Pacific Division champion Clippers the fourth seed in the Western Conference playoffs.
Butler hit 4-of-7 attempts from 3-point range and Chris Paul added eight points and 11 assists in the victory.
Will Barton led Portland with 17 points and Joel Freeland came off the bench to score 13. The Blazers fell for the 12th consecutive game.
Los Angeles shot 46.8 percent from the field to Portland's 41.1 percent and led 54-37 at halftime after the Blazers scored just 13 points in the second quarter.