Among the shoppers gathered for the 9 a.m. opening Friday was 84-year-old Marion Hango of Clackamas, who said she wanted to be there to support the workers.
"I've been thinking about it for several days, just like everybody else," she said. "But I felt it was necessary, not just for me, but for everybody else, the people who work here.
"My daughter was going to order something off the Internet for my grandson, and I said, 'No, I'm going to buy it at the mall, just to help them,'" she said.
The mall was closed Wednesday and Thursday as officers worked on their investigation and contractors repaired damage.
The shooter, Jacob Tyler Roberts, killed himself after the attack Tuesday afternoon, authorities have said.
Security precautions were intensified for the reopening, the Clackamas County sheriff's office said.
At a news conference before the reopening, the mall's general manager, Dennis Curtis, declined to estimate how much the closure had cost in lost sales.
"It's really hard at this time to focus on profits and sales," he said.