The schoolboy, dressed in a flat cap, scarf and long coat, stole a purse from a shopper while his much taller accomplice distracted her.
Victim Caroline Robinson, 32, from Thorpe Hesley in Rotherham, was robbed when she was waiting at a till in a branch of Poundland in the town centre with her children.
The purse was later found 12 miles away in Doncaster.
However, the contents – including a quantity of cash and a picture of her baby daughter while she was in intensive care – were missing.
Mrs Robinson said: “The boy must have been only about six or seven and he went behind me and took the purse from my handbag which was hung on my daughter’s pram.”
Mrs Robinson said she is also now too scared to take her children into Rotherham town centre. She added: “It would be bad enough if it was an adult, but you just wouldn’t expect that of a child.
“They’re preying on the vulnerable, like people with prams. I was a sitting duck.”
South Yorkshire Police have released CCTV of the odd pair to try to identify and track them down. Anyone with information is asked to contact officers by calling 101.
A Rotherham Council spokesman the town has a “very low crime rate”, adding that the centre has a “constant police and council presence”.