Cats and chihuahuas can make excellent companions due to their similar size and the chihuahua's affectionate nature. If you want these pets to bond successfully, you will need to begin socialising the chihuahua with the cat as soon as you get it home. An undisciplined chihuahua can develop some unruly habits, and your cat may exhibit aggressive or territorial behaviours if you fail to introduce the animals in a cautious and patient manner.
Begin obedience training before allowing your chihuahua to interact with your cat. Chihuahuas -- especially males -- love to establish themselves as pack leaders, and may exercise aggression toward other animals if they believe themselves to be dominant. You can eradicate this behaviour with obedience training. Spend up to an hour each day training your chihuahua to sit, stay, heel and perform other acts of obedience using puppy treats as rewards. This will establish you as the pack leader.
Introduce your chihuahuas to your cat one at a time, if dealing with multiple puppies. This will create a more controlled environment, and allow you to better supervise the situation. Always place your dogs on a leash when introducing them to your cat, and hold it tightly to prevent the situation from getting out of control.
Recruit a trusted friend or relative to assist you during the introduction. For the first few supervised interactions, you will need one person to hold the dog leash and one person to hold the cat. Since the chihuahua is a small breed of dog, cats will sometimes serve as the aggressor, attempting to attack the dog, especially if the dog begins to bark or behave erratically. For this reason, you must carefully supervise both animals.
Conclude the interaction immediately if either animal assumes a pouncing position, begins to hiss or growl, or stares at the other with quiet intensity. These are all indicators of aggression, and you must separate the animals before a fight breaks out. You can try again the next day. If both animals appear calm, allow them to interact, sniff one another and become acquainted, all while keeping a close grasp on each.
Alternate between your chihuahuas, if introducing more than one. Do not allow more than one chihuahua to interact with your cat simultaneously until every dog demonstrates calmness and comfort around the cat. The cat must also demonstrate a complete lack of aggression.
Reward each animal for a positive interaction. If the two animals get along, present them each with an appropriate dog or cat treat as a means of positive reinforcement. If they fail to get along, keep introducing them for a couple of minutes each day, all while keeping a firm hold on each. If, after several interactions, they still show aggression or unease around one another, continue the obedience training with your chihuahua, have both animals spayed or neutered, and never allow unsupervised interactions.
If your cat has a fondness for scratching, try clipping its nails before introducing it to your chihuahuas. Even in a controlled environment, you cannot rule out the possibility that your cat may suddenly swipe its claw and strike you or your dog.