Diogu, a second-year reserve from Arizona State, was 7-of-7 from the field and hit all five of his free throws in 24 minutes.
All of Indiana's starters scored in double figures, led by Troy Murphy, who had 14 points and fouled out in the third quarter. Murphy, a center with outside range, hit consecutive 3-pointers in the third quarter to give Indiana an 84-63 lead. He also hit a 3-pointer in the first half.
Jermaine O'Neal scored 10 of his 13 points in the first half to help Indiana take a 62-52 lead. Danny Granger had 13 points, while Mike Dunleavy and Jamaal Tinsley both added 10 for the Pacers.
Adam Haluska, a second-round draft pick out of Iowa, led the Hornets with 20 points. He hit three 3-pointers in improving his preseason scoring average to 16.0.
David West led New Orleans' starters with 14 points, while Morris Peterson had 11 points and Tyson Chandler 10. Chris Paul had nine assists in 20 minutes.
Pacers guard Marquis Daniels missed the game with a bruised left knee.
New Orleans' Peja Stojakovic, returning from back surgery that caused him to miss most of last season, played only four minutes, missing his only shot.
The game was the first in New Orleans for the Hornets since their return to the city over the summer. They spent parts of the last two season in Oklahoma City, where they moved temporarily after Hurricane Katrina. The announced attendance was 7,736.