Generally speaking the Chihuahua is a very good tempered dog. Chihuahuas make a great companion dog because they form such a strong bond with their owners. They are also very fond of snuggling and sleeping under the covers with you on a cold night. Chihuahuas are extremely loyal to their owners and very eager to give and receive affection from them. They also make extremely good watch dogs, with their big ears and strong hearing Chihuahuas can alert you to the slightest noise.
While not known for their playfulness, chihuahuas are more than happy to do so with someone they trust. Chihuahuas will play fetch, tug-o-war, chase laser lights, run, hike with you, and they will even try to catch a Frisbee. When they are not playing Chihuahuas are quite content to just sit in your lap as long as you will let them. Chihuahuas get cold easily so they like to be next to their owners warm bodies as much as possible. Like most dogs, they will mirror whatever you want to do. If they cannot be in your lap or next to you, they will follow you around wherever you go. If you leave, your Chihuahua will sit anxiously by a window or a door awaiting your return.
An interesting observation that most Chihuahua owners make is that Chihuahuas seem to recognize their own breed. The do not tolerate other breeds as well as they do their own, and will even develop a pack mentality with other Chihuahuas, while remaining hostile towards other breeds; even other toy breeds. In order to deter this aggressiveness towards other dogs, it is important to socialize your Chihuahua as much as possible from the time they are a pup.
Because of their extremely small size, Chihuahuas are often times treated and disciplined differently than a bigger dog. Their aggression is often viewed as being cute or comical and so many owners do not correct their Chihuahuas as often when they are growling or barking or showing signs of aggression. Also because of their small size, they are easily scooped up into their owners arms when they are doing something wrong instead of being corrected. This excessive coddling can give the Chihuahua the wrong impression of what is acceptable behavior. To further encourage eccentric behavior, a lot of owners consider a Chihuahua a house dog "only", and so they do not get the proper socialization that other dogs may get. Because of this isolation and the differences in discipline and treatment a Chihuahua can develop into a very complicated dog. They can sometimes seem like a walking contradiction. They will be very loyal and friendly, but may suddenly become territorial and snappy. They will be eager to please, but hard to train. They are small, but will be aggressive towards other dogs. While these behaviors are can be corrected or prevented from developing, they are still not recommended for families with small children.