A 28-year-old man was arrested after police seized two parcels in the post containing around 50,000 diazepam tablets.
The packages were seized in greater Belfast yesterday.
Class A, B and C drugs were later discovered during further searches.
The man was released on bail pending forensic testing of the recovered drugs.
Detective Inspector Richard Thornton said: "Those involved in drugs criminality seek to line their own pockets at the expense of causing harm to others. They set out to ruin the communities that they live and operate in and they do not care about the damage that they cause, preying on those who are vulnerable."
He asked anyone with information about the use or supply of drugs to contact police on 101.
