The nine-second clip was filmed at the James Watt in Greenock, Inverclyde, and uploaded to Facebook yesterday (19 July).
It shows the rat scuttling across a seat of the leather booths in the pub, before jumping below the table and disappearing from sight.
Facebook users expressed their disgust at the footage.
One wrote: "I don't eat out of there but I'll never drink in there either, f*** that!", while another said: “Oh my god, that’s vile.”
A JDW spokesperson said the rat had come in from the street due to nearby demolition work.
Spokesman Eddie Gershon told the Daily Record: "A single rat literally walked in the open front door of the pub. The pub closed early at 10pm and the area was cleaned.
"Our pest control team has been working in the pub this morning (20 July) and confirmed that there are no issues. They will return to check the situation again next week."
He continued: "The pub is open and trading as usual. We apologise to customers for any inconvenience caused."
Earlier this week, a cancer patient criticised the pub chain after being thrown out of one of its Liverpool sites for "touting".
Peter Quinn claimed that the duty manager asked him to leave the premises for trying to raise money for a variety of charities including Help for Heroes and Cancer Research.
In May, a Lancashire pub was forced to close for three days after rodent droppings were found throughout the site.