Regina Cat Rescue says they are at full capacity and need homes for roughly 175 cats and kittens.
RCR is a non-profit organization that relies entirely on volunteers, donations and fundraisers. It doesn't have a central facility, so volunteers are needed to foster cats until they can be adopted.
"We only have so much available foster care space and only so much money that we can raise and put towards caring for these animals, so we have had to decline rescues," Alanna Whippler, volunteer co-ordinator at RCR, told CBC News.
"You feel bad about it, but we are stretched quite thin.
"We're still getting lots of requests every day to take in cats. We've just decided we were at the point where we had to start saying no just to make sure that we can take care of the cats we have."
Whippler added resources are tight even when RCR isn't at full capacity.
"The demand that we get for taking on rescued cats pretty much exceeds our ability to cover all the vet care and cover all the costs associated with looking after several hundred animals a year."
RCR's veterinary bill for 2016 was about $160,000, Whippler said.
Ways to help
RCR also runs a trap, neuter and return program that involves spaying or neutering non-tame cats that live on the street, to reduce feral cat populations.
There are several ways the public can help, according to Whippler.
"People can help us out by adopting a cat through us, by making donations to Regina Cat Rescue to help us out with our vet care costs, by offering to foster a cat, and also by volunteering for fundraising activities and some of our other activities we get in to."
Anyone who finds a a cat, or any animal, that needs immediate attention is urged to call the Regina Humane Society.