The suspicious package was found at a security checkpoint in the U.S. departures area early Sunday morning, said Jean-Pierre Brabant, a Montreal police spokesman.
The items in the bag were not explosives, but parts of a potential device, said police. They did not say specifically what parts were found.
The suspect was detained but had not yet been questioned or charged, said Ian Lafreniere, another police spokesman.
Police blocked off a residential area near the airport Sunday evening, and about 20 residents were ordered from their homes. At least a dozen emergency vehicles were on the scene while police searched the 71-year-old man's home.
The U.S. screening area of the airport was closed and a number of flights were delayed, but resumed later on Sunday.