It is believed the elderly farmer may have been checking on cattle when he collapsed and died.
A neighbour reported the pensioner missing around midnight on Tuesday. He had become concerned after not seeing him for a couple of days and had called at his home. There was no sign of the pensioner.
Police searched the area around the house but it was dark at the time. They were assisted by a Northern Ireland Fire and Rescue Service crew equipped with a thermal imaging camera.
At first light today a PSNI helicopter joined the search of the area, which is close to the Border, while gardai checked adjoining land in County Cavan. The man's body was found in a field near his home around 10.15am and was taken away for a post mortem.
His name isn't being released until his family has been informed.