The operation was carried out in the Lambfield Drive area of Dungannon on the evening of Monday 24th October.
The men and woman have been arrested on suspicion of a number of offences including possession of a class B drug, possession of a class B drug with intent to supply, concealing criminal property and driving whilst disqualified.
All three remain in custody assisting police with their enquiries.
A police spokesperson said: “As a result of a follow, up search in the Lambfield Drive area today, Tuesday, October 25, police have recovered a suspected firearm and ammunition which has now been taken away for further forensic examination.
!Anyone with any information about the use or supply of illegal drugs should contact their local station on 101 or Crimestoppers anonymously on 0800 555 111.”