Health inspectors found seven of the insects in areas used to prep food and wash up.
Westminster Council said: "Appropriate treatment methods must be used to eliminate these pests."
The restaurant, which charges £165 for a set menu with wine pairings, was also given a two-star hygiene rating, a fall from their previous five-star rating in 2013.
Ramsay is best-known for his Kitchen Nightmares series, in which he critiques and revamps failing restaurants.
This comes in the same week that the celebrity chef lost a High Court battle over the rent for a £640,000-per-year London pub which he claimed was agreed using signature forged with a "ghost-writing machine".
As part of a case aganist his father-in-law Christopher Hutcheson, who Ramsay sacked as his agent in 2010, the chef claimed that his signature on the York & Albany was "not lawfully authorised".
Ramsay's spokesperson Jo Livingston said: "We invest considerable time and resource in maintaining the highest possible food hygiene standards and have an excellent track record. In addition to our own in-house measures, we work with an independent auditor who regularly inspects all our restaurants.
"While this was an isolated incident, we took immediate steps to resolve the problem and are confident the restaurant is back to our usual exacting standards".Reuse content