The men, aged 21, 22 and 33 were arrested along with a 45-year-old woman on Thursday after police seized a large quantity of diazepam tablets in north Belfast.
The men face a number of drug offences.
They are due to appear at Belfast Magistrates' Court on Saturday.
The 21-year-old is also charged with possessing a firearm in suspicious circumstances.
The 22-year-old man is also charged with money laundering.
On Friday, a 45-year-old woman appeared in court charged with conspiracy to supply class C drugs.
Kelly Clarke, of Ardoyne Road in Belfast, also faced a charge of being concerned in the supply of diazepam between 1 August last year and 16 April this year.
She was granted bail.
Three men have been charged in connection with a police investigation into the supply of prescription drugs into Northern Ireland.