The package was discovered by an airport employee at 5:45 a.m., and police were called to the scene.
A spokesperson for the airport said the police tactical team set up a large security perimeter at 10:35 a.m. so officers could analyze the package.
Police said the package was removed at around 1:00 p.m. and the contents have been sent to a lab for tests.
"We didn't want to take any risk and any chances, because when there's an airport, there's a lot of people, so that's why we evacuated certain parts," said Montreal police spokesman, Const. Jean-Pierre Brabant.
Sixteen flights heading to American destinations were unable to take off during the police operation.
The perimeter was lifted and service has resumed, however, there were delays for passengers at U.S. customs checkpoints.