The girl was stabbed eight times in the "random attack" on Monday when a man allegedly approached her and her mother in Leicester Square.
It was initially believed the girl's mother, 34, was also hurt, but police said blood from her daughter's injuries had been mistaken for injuries of her own.
The Department of Foreign Affairs and Trade on Wednesday confirmed it was providing consular assistance to two Australians in London.
The family is understood to be from NSW, the ABC reported.
A man faced court on Tuesday charged with the attempted murder of the girl and possession of a bladed article in a public place.
Ioan Pintaru, 32, was a Romanian citizen of no fixed address, Westminster Magistrates Court was told.
Prosecutor David Burns said the girl and her mother were in the Leicester Square area as tourists just before the incident, which he said was a "random attack on a child".
"The defendant has approached the 11-year-old girl, placed her into a headlock and he has then stabbed her eight times to the body," Burns said.
She was wounded in the face, shoulder, wrist and neck, he said.
The court heard members of the public intervened and when police arrived they found a man being held on the ground.
Police on Monday said the girl was taken to hospital with serious but non-life threatening injuries.
There was no suggestion the attack was terrorism-related, police said.
Pintaru was not asked to enter any pleas and was remanded in custody before his next court hearing at the Old Bailey on September 10.
with PA and Reuters
