In a case which cost the RSPCA over £110,000, Elsie Nash, aged 79, was told that her well-intentioned actions had led to unnecessary suffering.
Animal welfare experts found that many of the 40 cats had respiratory and ear infections, and criticised the state of the three-bedroom house.
Nash will be sentenced next month. But, speaking outside Birmingham Magistrates Court, she refused to accept that she had acted wrongly, and said she had no regrets.
“My life is my own, and the cats were my life,” she said.
“They couldn’t care less about the welfare of cats.”
The court was shown a video of the house, in Kingsbury Road, Erdington, which was run-down and dominated by cats.
Nash was found guilty of 13 charges of cruelty, but not guilty over the death of one cat following a nose infection.
Judge Qureshi warned that he would be considering all his options for sentencing - including prison .