Cheltenham bookmakers, Paddy Power, were robbed by a knife-wielding man who stole £550.
The robbery at the High Street betting shop took place on Good Friday.
The man carrying a kitchen knife demanded the cashier handed over money at around 6.40pm.
He left the shop with between £500 and £600 in cash before running off in the direction of HMV.
Gloucestershire Police confirmed no one was injured in the incident.
The offender is described as male, white, in his 20s, around 6ft tall with blonde hair.
He was of slim build and spoke with a local accent.
He was wearing dark clothes with a scarf covering his face apart from his eyes and was carrying an orange/brown plastic carrier bag.
Anyone with information that could help the investigation should call police on 101 quoting incident 370 of March 29.
You can also remain anonymous and contact the charity Crimestoppers on 0800 555 111, or via uk.org/">www.crimestoppers-uk.org. In some cases Crimestoppers offer rewards of up to £1000 where information leads to a conviction.
