The offender made off with foreign currency after the incident at a Thomson store on Derby Street in Leek, Staffordshire.
The man entered the shop at around 5.15pm on Wednesday (July 13) and threatened the travel consultant with the weapon, according to the Leek Post and Times.
He then made off with euros and dollars.
A Staffordshire Police spokesperson said: "Officers are investigating a robbery at a travel agents in Derby Street, Leek in which the cashier was threatened with a bladed instrument.
"The offender entered Thomson at around 5.15pm on Wednesday 13 July and stole cash from the Bureau de Change before making off.
"The cashier was left shaken by the incident but was not injured."
Police have described the man as a white male aged between his late 30s to early 40s.
He was also reported to be wearing dark lensed glasses, a blue jacket and carrying a plastic bag.
Anyone with any information is asked to call Staffordshire Police on 101 - quoting incident 520 of July 13.
Alternatively, you can contact Crimestoppers, anonymously on 0800 555 111, or via the anonymous online form at www.crimestoppers-uk.org.
