The man and an accomplice were both carrying what police have described as “six-inch bladed weapons” during the incident at the Fortune Cookie restaurant in Great Ayton.
They entered the premises at about 7.50pm and threatened staff with the weapons before making off on foot with an amount of cash.
North Yorkshire Police’s Det Sgt Michele Fawcett said: “Thankfully, no-one was injured, however the staff were terrified and have been left extremely shaken.
“This was a very serious incident and we are doing all we can to identify the offenders.
“We are asking anyone who witnessed the incident, saw anything suspicious in the area at the time or may have any dashcam footage that may assist, to contact police.
“If you think you might have seen the two men yesterday evening in the area, please also contact police.
“Any piece of information you can provide could assist this investigation.”
The man in the vampire mask is described as medium build and was dressed in camouflage trousers, a blue or grey Adidas jacket and red gloves.
His accomplice is said to have been of large build and spoke with a Teesside accent.
He was wearing an olive green jacket and had a blue scarf or snood covering his face.
Anyone with information is asked to ring North Yorkshire Police on 101 or Crimestoppers anonymously on 0800 555111.