The museum, which remains open, houses a century of scouting history, including the largest collection of Norman Rockwell scouting art in the world.
The quake caused at least five cracks inside and outside. Several are hairline cracks, but one or two appear to be about an inch thick.
The damage to the museum from the May 16 quake that was centered in North Arlington was previously unreported.
"I thought, 'Wow, an earthquake,'" said museum director Janice Babineaux.
People inside the museum at the time of the quake felt the ground shake.
"The employees that were here reported that they felt some movement," Babineaux said. "They thought it was a wreck -- a large vehicle, maybe an 18-wheeler or something."
The Rockwell paintings were undisturbed.
Engineers inspected the 53,000-square-foot building and determined there was no apparent structural damage, Boy Scout administrators said.
"We think at this point it's just cosmetic," Babineaux said.
The scouts said they were prepared. The building was insured.
The museum draws about 25,000 visitors a year.
Repairs should start soon.
"It could have been much worse," Babineaux said. "So we're grateful and thankful that it wasn't."
The National Scouting Museum was founded in New Jersey in 1960 and moved next door to the Boy Scouts of America headquarters in Irving in 2002.