By Friday, 58 cat owners had claimed a voucher to have their pet desexed free of charge since the campaign began on September 1.
Queenstown Cat Rescue co-founder Ms de Reus said the number was expected to increase to "perhaps 80" by the end of this month.
Of the vouchers claimed, 27 were for female cats and 31 for males throughout the Queenstown and Cromwell area.
"Some of these people have also claimed that their cat has previously had kittens."
Most people listed inability to afford desexing their cat as the reason for registering and Ms de Reus said the campaign would take pressure off the group and vets.
"It's been a great response and it will mean that there will be less pressure on ourselves and our local vets in Queenstown and Cromwell when it comes to taking on unwanted kittens to put up for adoption. I feel that not only will our community benefit from this, but it will make a significant difference on the quality of life that these ex-breeding cats will lead."
The group raised $7000. It staged the campaign in September so the warmer weather would help aid the cats recovery.
Cat owners could register their pets for the free desexing by calling Ms de Reus on 027 2083725.
