The two black pups were thrown from a red car behind Windsor Terrace, in Grangetown, in front of horrified children.
The dogs, less than a year old, were rescued by boys who had been playing in the street and watched in horror as the dogs were dumped.
Jack Minto, 11, a pupil at Southmoor School, and nine-year-old Adam Wilkinson, who goes to Grangetown School, were appalled and rushed to the dogs' aid.
The pair took the dogs to charity Animal Krackers, in Windsor Terrace.
Andrea Parkin, manager of Animal Krackers, said: "People like that should not be allowed to keep pets. I'm just glad Jack and Adam were there to rescue them or who knows what could have happened.
"The boys were concerned. It's just horrific to think someone could do something like this to defenceless animals."
She added: "The dogs were taken in by foster parents but we are looking for a new home for them."
Andrea added: "They've had a clean bill of health so we don't think they've been badly treated until dumped."
Andrea and co-founder of Animal Krackers, Sue Hardy are spearheading a campaign to get an animal rescue shelter for the city.
* If you can offer one or both of the dogs a new home, ring Animal Krackers on 564 1812.