The video shows a masked person brandishing what appears to be a gun before taking cash from the till at the Gulf filling station on Glasgow Road.
Police said the lone female staff attendant was "terrified" by the incident, which occurred at about 21:30 on 21 October.
Officers continue to investigate and have appealed for witnesses.
The suspect, thought to be a man, was about 6ft tall, between 16 and 30 years of age, was of slim or medium build and was wearing dark clothing including a black hoodie with the hood up.
Det Insp Graeme Hendry said officers had been making "extensive" inquiries.
He said: "The response from people in Denny has been magnificent and I am grateful to them, however we have still to identify the person.
"I am sure that someone knows the identity of the person and that they too will be alarmed by the trauma this crime caused the staff at the garage."
Police have issued CCTV footage of an armed robbery at a petrol station in Denny in a bid to catch the culprit.