The video taken outside a grilled chicken shop in Sabaneta, Colombia, shows one employee blasting the man with a hose, whilst another pushes him from behind - causing him to fall head first into the serving counter and knock himself unconscious.
The man was then transported to Venancio Diaz Diaz hospital, where he was released a short time later.
According to video site Live Leak, police arrived shortly after the incident to reports of a fight, and found the old man had regained consciousness.
The mayor of the town of Sabaneta, where the incident took place, has condemned the employees actions, stating that such treatment of any person will not be tolerated.
Footage was recorded on a cell phone, which quickly cuts out after the elderly man is knocked unconscious.
At least one of the fast food workers - the one who pushed the old man over - is believed to be under investigation following the incident, with police saying he is likely to be charged with assault.