Police hold grave concerns for a man who was last seen falling over a waterfall in the NSW New England region.

The 37-year-old was travelling from Armidale to Kempsey with friends just before 6pm on Sunday night, when they stopped for a break at Ebor Falls, about 80km east of Armidale.

Witnesses say the man walked to a rock ledge at the top of the falls, but then lost his balance and fell head first over the edge.

Police and State Emergency Service crews conducted a search for the man before the operation was suspended at nightfall.

Police said the search will resume at 8am on Monday. However, poor weather conditions and heavy water flow, due to the falls being in flood, could hamper their efforts.