The 16-year-old Idaho youth, whose name was not released, was taken into custody at his home in Meridian Friday, the Idaho Statesman reported.
The newspaper said in recent days at least 17 bomb threats were made to schools and businesses in the Idaho communities of Meridian, Boise, Kuna, Caldwell, Twin Falls, Nampa and Eagle.
Each threat led authorities to evacuate the targeted school or business while the area was searched.
Investigators allege the two boys met several months ago on an online gaming site and worked out the threat scheme together.
The youths allegedly admitted making prank calls to restaurants and other businesses before advancing to bomb threats this week, the Statesman said.
The Meridian teen is accused of providing the target locations and phone numbers to the Australian teen, who then placed calls by phone and through a computer network.
"These went well beyond a hoax or prank to what I would call domestic terrorist threats," Meridian Police Chief Jeff Lavey said. "From the emotional strain on teachers, students and parents to the time and money expended by our officers and sales lost by businesses forced to evacuate, these threats take an incredible toll on our communities."
Ada County Sheriff's Detective Sgt. Steve Bartlett said there was no evidence to suggest the Meridian boy had the means to carry out the threats. But Bartlett said the boy intended to include medical facilities in future threats.
Ada County detectives were working with Australian law enforcement officials in Orange, New South Wales who have identified the other teen and confirmed his involvement, the Statesman said. The Australian boy could face criminal charges as well, the newspaper said.
"This is a great example of officers from multiple jurisdictions and even a foreign country sharing information and resources to manage a complex investigation and quickly take those responsible into custody," Ada County Sheriff Gary Raney said. "Making a threat is a felony whether you are a juvenile or adult. We take these calls very seriously. Anytime a threat is made, we will find the people responsible and hold them accountable."