Ty Nant Cat Sanctuary in Cymmer was broken into on 30 July and an 18-year-old man and 15-year-old boy have been charged in connection with the alleged burglary.
Three of the cats were found dead while others are still missing.
More than 1,250 people have since donated to the GoFundMe page online.
The initial fundraising target was £1,000.
A spokesman wrote on the sanctuary Facebook page: "We have been astounded by the level of support we have received."
They are now appealing for help in searching for the missing five cats and are offering a £100 reward for their safe return.
They are looking for a tortoiseshell and white cat, three black and white cats and a large tabby cat.
Ty Nant Cat Sanctuary was set up in 1990 in response to the growing problem of unwanted, stray and abandoned cats in the area. Since then hundreds of cats and kittens have passed through its care.
A fundraising campaign set up for a Neath Port Talbot cat sanctuary has collected more than £17,000 in just four days.