Yes, neutering a cat is permissible in Islam as long as it does not harm the animal. If the owner believes it is in the best interest of the cat to be neutered, it is allowed. It is important to ensure that the cat is not subjected to unnecessary harm, as mercy to all of Allah’s creation is incumbent upon every Muslim. The Prophet Muhammad (peace be upon him) said: “A woman entered the hellfire because of a cat which she tied up and did not feed.” (Sahih al-Bukhari)

Sources:

• Darulifta Birmingham
• Islam Q&A

And Allah knows best.