Linas Kleiza had 34 points for the Nuggets, who led by as many as 30 points.
The Blazers narrowed the gap in the final minutes with a 20-0 run capped by Travis Outlaw's layup that made it 114-121.
"When we took A.I. out (in the fourth quarter), we kind of lost our head," Nuggets coach George Karl said.
Outlaw led the Blazers with 23 points and six assists.
Shooting guard Brandon Roy did not play for the Blazers, although he did suit up. In Portland's 109-107 exhibition victory over Seattle on Wednesday, last season's Rookie of the Year played more minutes than planned by coach Nate McMillan.
At the start of fall camp, Roy had trouble with heel inflammation, which kept him out of 20 games last season.
Iverson, who has had a bruised left thigh, was uncertain for the game, but started and elicited cheers from the crowd when he was introduced.
Iverson had 17 first-half points. J.R. Smith scored off a pass from him to give the Nuggets a 58-47 lead.
Denver led 67-60 at the break, then went on a 17-3 run to start the second half, capped by Iverson's 3-pointer to make it 84-63.
Kleiza's 3-pointer gave Denver a 104-80 lead before the third quarter was over.
"I think you tune yourself up and get that edge for playing by playing basketball games," Karl said.
Carmelo Anthony suited up for the Nuggets but did not play.
The game was held inside the Deschutes County Expo Center in Redmond, about 150 miles from Portland. Fire alarms sounded for a time in the second quarter, but the teams played on.
It was the preseason finale for both teams. Portland opens the regular season next Tuesday at San Antonio, while the Nuggets host Seattle on Halloween.
"We had a good camp and I liked our effort," Blazers coach Nate McMillan said. "We showed some good things. I like our energy and I like this team."