It happened in the Cullybackey area of Ballymena in the early hours of this morning, Tuesday, October 1.
At approximately 12.30 am, police received a report of a robbery of a taxi driver in the area.
Two men got into the taxi in the Spence Crescent area and the taxi driver dropped them off in the Dunclug Park area.
When the vehicle had stopped one of the men presented a knife and demanded money. Both men made off on foot with a sum of money.
This was an extremely distressing time for the taxi driver who has been left badly shaken. No one should feel unsafe in their work environment.
A 21 year old man has been arrested. He remains in custody at this time and is assisting with enquiries.
Detective Sergeant Crothers said: “I would ask anyone who was in the area between midnight and 12.30am and witnessed anyone acting in a suspicious manner to contact detectives at Ballymena PSNI station on the non-emergency number 101, quoting reference 31 01/10/19.
“Alternatively, information can also be provided to the independent charity Crimestoppers on 0800 555 111, which is 100% anonymous and gives people the power to speak up and stop crime.