Officials say someone phoned in a bomb threat to the airport which prompted then to investigate.
Airport officials say the package was found around 2:30 p.m. near the atrium in the airport food court.
Boise Police and the TSA investigated the package for two hours before re-opening the airport at 4:30 p.m.
Officials called the package a "credible threat", but didn't elaborate on details.
The TSA security checkpoint was also closed. Hundreds of passengers waited outside the checkpoint for police to finish investigating.
The checkpoint is now open again, and passengers are being screened.
The passengers we talked to were frustrated, but most were accepting the delay.
"I appreciate that they are trying to keep us safe," Brent McNeill told us. "It is an inconvenience, but it is better than the alternative."