The ferrets were found under a bush in a field in Hayle on Sunday 25 July at around 10am.
A member of the public spotted them in a cat carrier before ringing the animal welfare charity.
RSPCA Animal Rescue Officer Megan Higgins collected the ferrets, which are not microchipped, and is now appealing for information to find out what happened to them.
She said: “These poor ferrets were found dumped in a cage-style cat carrier without food or water that had been thoughtlessly discarded in a field.
“It was a hot day and they had been left exposed to the elements without a thought for their welfare. Thankfully they were found and are now getting some much needed care and attention from the teams at RSPCA Little Valley Animal Shelter and RSPCA West Hatch Animal Centre.
“I am now appealing for information to see if anyone saw anything unusual in the area, or if anyone recognises the ferrets, to please call us on 0300 123 8018.”
The RSPCA recently launched a new campaign to ‘Cancel Out Cruelty’ as figures showed there were 1,095 reports of deliberate cruelty to animals in Cornwall in the last five years.
The charity has released the figures- which you can view on an interactive Cruelty Map - as part of its Cancel Out Cruelty campaign, to raise funds to keep its rescue teams out on the frontline saving animals in desperate need of help and to raise awareness about how we can all help stamp out cruelty for good.