Look carefully and they are not difficult to spot, scuttling across the lawns or along hedges in broad daylight.
"Now that we've seen one, it disgusts us," declared 19-year-old student Alexandre, as she enjoyed the gardens with her friend Ken.
Ken, 22, is more sanguine. "We're not far from the banks of the river. It's warm. They come for food," he said, a bowl of rice in one hand.
"As long as they don't come up to me, it doesn't bother me," he added.
The gardens are an oasis of peace and tranquility amid the bustle of the city, a chance for tourists to relax and bask in the sunshine.
But they also represent a prime opportunity for the hungry rodents.
The rats have become so emboldened by the rich pickings on offer that they are now a regular sight.
"There's so much rubbish, it's quite dirty. There are cigarette stubs everywhere and leftover food," Ariane Dalle, an artistic director who works nearby and regularly has her lunch in the gardens, told AFP.
"The problem is that people don't have respect for the environment," she said, pointing to the rubbish littering the grass despite numerous nearby bins.
German visitor Ralf Franckemoelle, 44, who was in the gardens having a sandwich with his family, did not seem to be too bothered by the animal visitors.
"It's worse elsewhere. There are rats everywhere," he said, adding that he did not find the Tuileries particularly dirty.
- Two rats for every Parisian -
According to officials at the Louvre, rats are present all year but are more prevalent in summer because they are attracted by the availability of food from tourists' picnics.
"Every two months, the gardens undergo a pest control process and in summer that happens each month," Louvre spokeswoman Elise Guillou told AFP.
"When the proliferation is at its worst, as it is at the moment, the (pest control) firm is immediately alerted by the museum in order to react as quickly as possible," she said.
The city authorities carried out their own annual pest control exercise between April 14 and June 13.
But, with its thousands of underground car parks, construction sites, cellars and sewers, Paris is the perfect breeding ground.
According to Frederic Devanlay, of pest control firm Avipur, the city has seen a resurgence in the rat population over the past eight years.
Although it would be impossible to produce an exact figure, Devanlay estimated there to be at least two rats for every Parisian.
In addition to the nuisance they cause, rats also pose a serious threat to human health.
Weil's disease, which can be fatal, is transmitted through skin contact with rat urine.
"They are used to people and are coming ever more into contact with humans," Devanlay added.
And he warned that they were increasingly developing resistance to the chemicals used in pest control.