Police have seized drugs and cash after forcing their way into a house in the Harryville area of Ballymena.
They said the search on Thursday followed "numerous reports from the community about concerns of drug dealing".
A 47-year-old man was arrested at the house and remains in custody.
The Class A drugs that were discovered are believed to be morphine tablets, while mobile phones were also seized.
Police have said "the investigation is ongoing with forensic enquiries to conduct and mobile devices to be interrogated".