The Rainbow Animal Shelter in Eglinton says every available space is used up and it's had to send several dogs to kennels elsewhere - forcing the charity's monthly costs up by a whopping £1,540.
Speaking about the annual scourge of people abandoning Christmas pets, spokeswoman Helen Davis said: "People are still seen throwing dogs out of cars to abandon them but they should contact ourselves or Derry City Council's dog pound. The pound might put the animals down after six days but either way it is kinder than leaving them on the streets."
Helen said the centre had been inundated with callers reporting unwanted or stray animals.
"Normally we receive five calls a day regarding unwanted animals or strays but since Christmas we would almost deal with that number every hour.
"We are dealing with a lot more strays than usual which has placed us under added pressure as we just don't have the room. We have had to ask local kennels to take some of our dogs, although they can't take those which haven't been vaccinated. This is costing us £10 per dog per day and we currently have six dogs kennelled."
The centre can cater for a maximum of 23 dogs and, Helen revealed: "As we have reached the limit we have one dog living in a bathroom and one living in reception!"
The Rainbow Animal Shelter rehomes 500 dogs and cats annually. The staff of 12 volunteers and part-time workers are currently working at full capacity and relying on extra volunteers to help walk the dogs.
Helen said: "If anyone has a few hours they could spare over their holidays to walk the dogs it would make a big difference."
She also appealed to anyone thinking of adopting a cat to consider choosing one of the many adult cats housed at the Rainbow shelter.
"It can be difficult to rehome adult cats as people prefer kittens, but we have many who are trained to use a litter tray already.
"Our dogs are also all neutered, microchipped, wormed and de-flead also."
If you can spare a few hours or are seeking to adopt a pet then the Rainbow Animal Shelter can be contacted on 028 71 812882 or on www.rainbowrehoming.com/adopt