New Orleans, which dealt away its best player in Chris Paul prior to the start of the season, has won its first two games of the campaign.
Boston was within nine to start the final period, but surrendered a six-point New Orleans run early in the fourth quarter.
Jack scored 21 points and Landry had 20 along with 10 rebounds. New Orleans maintained its advantage in part by hitting 21-of-25 from the foul line.
Ray Allen scored 15 points for the Celtics, who have lost their first two games of the season.