Popper, 39, was arrested Tuesday afternoon on Interstate 90 near the Spokane/Lincoln county line, the Washington State Patrol said.
Inside the black Mercedes SUV, officers found a cache of weapons and a small amount of marijuana, the Patrol said.
Popper, who lives in Snohomish, Wash., is the owner of the vehicle, which was being driven by Brian Gourgeois, 34, of Austin, Texas, said state patrol Trooper Jeff Sevigney.
Sevigney confirmed that Popper was a member of the popular band and that the pair was traveling from Texas to Washington
While the two men were administratively booked into the Adams County Jail in Ritzville, they were released on their own recognizance, Sevigney said. That's because Popper lives in the state and the crimes involved are misdemeanors, Sevigney said.
Gourgeois was placed under arrest for reckless driving and, after troopers reportedly smelled marijuana, Popper was arrested for drug possession, the Patrol said.
A police dog searched the vehicle, finding numerous hidden compartments. Inside those compartments were four rifles, nine handguns and a switchblade knife. They also found a Taser and night vision goggles.
Popper told officers he collected weapons, the Patrol said.
The vehicle also had flashing emergency headlights, a siren and a public address system, the Patrol said.
"Popper indicated to troopers that he had installed these items in his vehicle because (in the event of a natural disaster) he didn't want to be left behind," the Patrol said.
Officers also recovered a small amount of marijuana and a marijuana pipe. The vehicle was seized.
Popper achieved fame as a harmonica player and frontman for Blues Traveler. The band won a Grammy award in 1996 for the song "Run-around," which Popper composed.
Popper recently formed a group called The John Popper Project with DJ Logic, which released an album in 2006 and is scheduled to go on the road later this month.