Hong Kong Customs says it seized about 20 kilograms of suspected MDMA worth HK$4 million at the airport on Thursday.
A 31-year-old woman arriving from Vancouver was arrested after officers found the drugs in her checked luggage.
An investigation is ongoing.
Customs said it would continue targeting drug trafficking through intelligence-led enforcement and risk-based screening, particularly in high-risk regions.
The public is urged not to carry unknown items or engage in drug trafficking for money.
Trafficking dangerous drugs carries a maximum penalty of HK$5 million and life imprisonment under the Dangerous Drugs Ordinance.
