Mike Dunleavy had 14 points, Danny Granger scored 12 and Troy Murphy grabbed 12 rebounds for the Pacers, who improved to 2-0 this preseason under new coach Jim O'Brien.
Seattle rookie Kevin Durant, the second overall pick in the NBA Draft, had 21 points on 6-of-13 shooting from the field. Rookie Jeff Green, the fifth pick in the draft, scored 14.
The SuperSonics (1-2), who trailed by as many as 12 points in the first half, got within 78-73 early in the fourth quarter following consecutive baskets by Mouhamed Sene.
Indiana used an 8-0 run to extend its lead to 90-77 with five minutes left. Diener, who started in place of injured guard Jamaal Tinsley, hit two straight jumpers during the spurt.
In the first quarter, Durant's 3-pointer and Green's layup gave the Sonics a 20-15 advantage. The Pacers answered with a 10-0 run, which was capped by Granger's 3-pointer, to jump ahead by five points.
Indiana stretched its lead to 12 points following Dunleavy's 3-pointer late in the second quarter. The Sonics cut the deficit to 55-45 on Green's layup to end the half.
O'Neal started for the Pacers after missing the team's opening preseason game against New Orleans with a sore left knee. ... Seattle G/F Damien Wilkins sprained his right ankle in the second quarter and did not return. ... Pacers G Kareem Rush didn't play in the second half because of a sore right Achilles'. He scored five points in the opening half. ... Tinsley (sore right shoulder) and C David Harrison (ankle) did not play. ... Sonics G Delonte West (lower back strain) did not play. ... Seattle played its third of four straight road games to begin the preseason. The Sonics play their first home game Oct. 20 against Houston.