The Canada Border Services Agency describes last week's seizure as "significant."
The agency says that during a routine inspection at the airport on Jan. 16, CBSA officers monitoring baggage being unloaded from a flight from Pakistan noticed one backpack that was heavy.
Upon further examination, the officers discovered six wrapped bricks inside the backpack.
The agency says the bricks contained a substance that tested positive for suspected heroin during field testing.
The packages were turned over to Peel Regional Police and the investigation is still ongoing but there's no immediate word of any arrests.
The agency says it made more than 62 heroin seizures in the Greater Toronto Area last year, with a total of almost 150 kilograms seized.
"Our officers are always on the lookout for illegal goods," said CBSA spokesman Goran Vragovic.
"CBSA officers will not tolerate the use of our international borders for smuggling illegal narcotics that are harmful to our communities."