Cat behavior encompasses the actions and reactions displayed by a cat in response to various stimuli and events. Cat behavior includes body language, elimination habits, aggression, play, communication, hunting, grooming, urine marking, and face rubbing. It varies among individuals, colonies, and breeds.

Communication and sociability can vary greatly among individual cats. In a family with many cats, the interactions can change depending on which individuals are present and how restricted the territory and resources are. One or more individuals may become aggressive: fighting may occur with the attack, resulting in scratches and deep bite wounds.

Kittens vocalize early in development. Some examples of different vocalizations are described below.

Cats rely strongly on body language to communicate. A cat may rub against an object or lick a person. Much of a cat's body language is through its tail, ears, head position, and back posture.

Observing how a cat holds its tail can give a good sense of the cat's current temperament.

When cats greet another cat in their vicinity, they can do a slow, languid, long blink to communicate affection if they trust the person or animal they are in contact with. One way to communicate love and trust to a cat is to say its name, get its attention, look it in the eyes and then slowly blink at it to emulate trust and love. They may return the gesture.

In a study of 18 cats, the cat behavior of several half-blinks followed by a prolonged eye narrowing or eye closure was found to be a positive emotional response. They show a specific set of feline behaviors: several half-blinks followed by prolonged eye narrowing or eye closure. When a familiar human slow-blinks towards a cat, the cat tends to approach the human more frequently than if the human has a neutral expression that avoids eye contact. This behavior may share features with the "genuine" human smile that involves the corners of the eyes narrowing.

A cat's ears can tell an observer what they are feeling, such as pain, fear, or when they sense danger. At times, one may notice cats to display an ear posture commonly referred to as "airplane ears." This is when their ears are rotated to the sides or angled backward. Cats have acute hearing, so when something scares them, their ears tend to pin to the side or back, and the further they are, the more terrified the cat is. It can be difficult to understand what emotion the cat is portraying with their ears, especially since their ears undergo the same pattern when the cat feels they are in danger/feeling defensive, where their ears pin flat to their heads or turn back. "Airplane" ears do not last that long, only until the moment of danger or fear is over. When cats are in pain or feeling sick, they will hold their ears low, rotated to the side. Cats also show feelings of playfulness and happiness when their ears are pointing forward, straight up. This means the cat is alert and content.