The male named Rusty was captured in a tree near a home in the Adams Morgan neighborhood Monday afternoon, said National Zoo spokeswoman Pamela Baker-Masson.
Senior curator Brandie Smith said animal keepers surrounded the area where he was found and called Rusty's name to calm him before capturing him in a net.
"We just had to approach him carefully," she said. "We are surprised by the distance he was able to cover."
The animal was taken to the zoo's animal hospital for a checkup and will remain there for several days.
How he escaped is still a mystery, though. Zoo officials began reviewing security footage Monday morning to see if there is any evidence of how Rusty escaped or whether he may have been taken by a human and then set loose.
Curators have cut back any long tree limbs that may have aided the skilled climber with the escape.
"There is no obvious point that Rusty could have gotten out of the enclosure," Smith said, adding that it had held red pandas for years. "We all know that young males like to test boundaries."
Unlike giant pandas, red pandas are not members of the bear family. Red pandas are slightly bigger than a domestic cat and look similar to a raccoon. They are listed as vulnerable in the wild and native to China. Scientists believe about 10,000 of the animals remain.
Rusty arrived at the zoo in April from a zoo in Lincoln, Neb., and was in quarantine for several weeks until he went on exhibit in early June. He will turn 1 year old in July.
Red pandas are highly territorial, so zoo officials did not believe he would have traveled far. Rusty, it seems, wanted to explore his new city.
Animal keepers discovered he was missing Monday morning and started searching the zoo at 8 a.m. The zoo began sending out messages about his disappearance Monday morning on Twitter in case someone saw him.
A spokeswoman said the zoo was "incredibly grateful" that a woman who lived nearby saw him, tweeted a picture and called the zoo. The woman apparently had to leave town on a trip Monday, so they couldn't thank her in person.
Zoo Director Dennis Kelly said officials will thoroughly review the incident and said it's rare for any animal to escape.
"We will not let this happen again," he said. "Before we put Rusty back, we'll go back over this exhibit with a fine tooth comb."
The female red panda remained on view in the leafy exhibit Monday, despite the hoopla over her mate.