Chancellor George Osborne's family cat, Freya, is being treated by vets after being "clipped" by a car near Downing Street.
The tabby's injuries are not serious, a spokesman said.
Freya has lived at No 11 Downing Street - the Chancellor's official residence - since 2010.
Her previous misadventures include being rescued by a charity worker after straying more than a mile from her Westminster home.
The cat, believed to be about five years old, is also reported to have gone missing from the family's home in Notting Hill in 2009.
Cats have become a familiar feature of life in Downing Street over the years.
David Cameron welcomed Larry into No 10 in 2011 to try to solve a recurring rodent problem.
Eyebrows were raised when Mr Osborne added a dog to his No 11 household in 2011. Lola, a young bichon frise, was said to be cat-friendly.
It is understood Freya was "clipped" at the Ministry of Defence end of Whitehall, but it is not yet clear whose car was involved.
She had to be taken to the vet, but is recovering and expected to be on her way home soon, a spokesman said.
The chancellor is said to be "very grateful" to those who came to the aid of his pet.