The robbery happened at Coral on Knaresborough Road in Harrogate at around 8pm on Thursday 31 July 2014.
CCTV images have now been released of the suspect.
The man used a knife to threaten a member of staff before leaving the premises with a quantity of money.
No one was injured as a result of the incident.
He is described as white and his face was covered by a dark garment and a dark hat. At the time, the man was wearing a dark jacket and carrying a dark holdall bag.
Detective Constable Fiona Ayre, of Harrogate CID, said: I am asking you to look at the images to see if you recognise the man captured on camera. If you can help to identify him, please contact the police immediately.
Thankfully noone was physically harmed as a result of the incident. However, the experience has naturally left the staff member very shaken.
The area around Coral was quite busy at the time of the robbery. I ask anyone who may have seen anything suspicious, and has not yet already contacted the police, to do so straight away.
Anyone who can help to identify the suspect should contact Harrogate CID on 101, select option 2 and ask for Fiona Ayre. Information can also be emailed to firstname.lastname@example.org
For those who would prefer to remain anonymous, details can be passed to Crimestoppers on 0800 555 111
Please quote reference number 12140128586.