Police said the High Court received a parcel containing unknown powder on Tuesday afternoon.
Officers from the Explosive Ordnance Disposal Bureau arrived to handle it, and investigations are ongoing. No one has been arrested so far.
In a statement, Justice Secretary Paul Lam said he is deeply concerned about the incident.
“In Hong Kong where the rule of law is upheld, no act of intimidation or violence which is against the law or constitutes contempt of court will be tolerated,” he wrote.
Lam added the government "will pursue seriously against any person who commits any such act and bring the culprit to justice in order to defend the integrity of the court, ensure the due administration of the justice and maintain public order".