The white and black female kitten has been named Mo, short for Moses and was tied inside a pink plastic basket with a piece of blue twine.
When the kitten was plucked to safety the basket was filling with water. The incident happened on the Leeds and Liverpool canal at Bramley, Leeds, on Saturday, September 10.
The boys, who are school friends, from Bramley, took her to one of their homes where a parent rang the RSPCA.
RSPCA inspector, Dave Holgate, said: “If it hadn’t been for the quick-thinking of these two young boys this kitten would certainly have drowned.
“Whoever did this condemned this kitten to death and I want to know who they are.”
The kitten was aged around nine weeks old at the time. She wasn’t micro-chipped or wearing a collar and ID so there is no way of tracing her owner.
Anyone with any information about the incident is urged to telephone the RSPCA on 0300 1234 999.