Got a feral (wild) cat? The SAFCC can help, they offer free workshops on how to humanely catch feral cats and have them spay/neutered. Referral services are offered for affordable; sometimes free spay/neuter options.
The San Antonio Humane Society offers spay and neuter services for pets at more affordable rates than private veterinary clinics. An appointment must be scheduled online in advance. Additionally, up to 10 feral cats a day can be spayed and neutered for free on select days. See their website for more info.
Organized by a group of veterinarians, SNIPSA’s mission is to rescue, rehabilitate, re-home adoptable animals and to encourage responsible pet ownership. The group provides free spay/neuter services to areas of San Antonio with the greatest need, such as with their program called the "Big Fix".