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Home > Dogs > Dog Breeds > American Mastiff Dog Breed: Info, Pictures, & Care Guide

American Mastiff Dog Breed: Info, Pictures, & Care Guide

brindle american mastiff male

The American Mastiff is a very large and powerful dog, often weighing as much if not more than its owner. Fortunately, they are known for their calm and mellow nature and are not considered an aggressive breed at all. However, they can be stubborn and highly independent, which makes training them a challenge, and you will certainly be unable to convince one to do something it doesn’t want to.

Breed Overview


28 – 36 inches


140 – 200 pounds


10 – 12 years


Fawn, apricot, brindle

Suitable for

Families with experience in training and socializing large breeds


Loyal, loving, calm, protective

Although it is a true mastiff breed, the American Mastiff suffers from less drool than most similar breeds, but you should still expect some natural drool formation.

Although the American Mastiff can make an excellent family pet that will get along with virtually everybody in or around the home, taking on a dog of this size is no small undertaking and you must be sure that you know what you are getting yourself into. You will have to feed them a lot and the breed is prone to some health problems, while also having a relatively short lifespan averaging 10-12 years. What’s more, as gentle as one may be, an American Mastiff can still weigh as much as 200 pounds so even an accidental bump can do some damage. Let’s get into all the details surrounding this gentle giant.

American Mastiff Characteristics

High-energy dogs will need a lot of mental and physical stimulation to stay happy and healthy, while low-energy dogs require minimal physical activity. It’s important when choosing a dog to make sure their energy levels match your lifestyle or vice versa.
Easy-to-train dogs are more skilled at learning prompts and actions quickly with minimal training. Dogs that are harder to train will require a bit more patience and practice.
Some dog breeds are prone to certain genetic health problems, and some more than others. This doesn’t mean that every dog will have these issues, but they have an increased risk, so it’s important to understand and prepare for any additional needs they may require.
Some breeds, due to their size or their breeds potential genetic health issues, have shorter lifespans than others. Proper exercise, nutrition, and hygiene also play an important role in the lifespan of your pet.
Some dog breeds are more social than others, both towards humans and other dogs. More social dogs have a tendency to run up to strangers for pets and scratches, while less social dogs shy away and are more cautious, even potentially aggressive. No matter the breed, it’s important to socialize your dog and expose them to lots of different situations.

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American Mastiff Puppies

The American Mastiff is a very large breed. While it isn’t one of the most popular breeds, the parent dogs and puppies eat a lot and take up a lot of room which, in turn, means that they can cost the breeder a lot of money before they are sold.

Ensure that you use a reputable breeder. Check with other owners of the same breed, take a look at the kennel club, and speak to local vets and other animal services. Although the size of the breed means that there aren’t too many American Mastiffs in circulation, you shouldn’t have to travel too far across the country to find a breeder.

When you do find a breeder, ask plenty of questions. A good breeder will have no issue answering your questions and they will want to ensure that you’re prepared to take on a dog of this size because they won’t want to have to take the dog back later. Ask to meet one or both parents. It is usually the mom that is available. Meeting her can give you an indication of how big the dog will get, as well as the kind of temperament and traits that mom will pass on to her puppies in the first few months.

When speaking to the breeder, ask for proof of the necessary health screening tests and other tests. Mastiffs are especially prone to joint dysplasia and having the parents screened can help prevent this condition from being passed from one generation to the next.

The size of the breed means that some owners are unable to cope with these dogs when they mature, and this means that you might find some in local shelters. Adopting a dog from a rescue costs less than buying and the cost does vary according to the shelter you go to.

Parent_breeds_American Mastiff
Image Credit: Left-  Anna Krivitskaya, Shutterstock |Right – Christian Mueller, Shutterstock

Temperament & Intelligence of the American Mastiff Dog

The American Mastiff is something of a gentle giant breed. They are not aggressive, despite having been bred to act as livestock guardians and for hunting large game. They do not require much exercise but they do need a lot of space.

They may not be overly friendly with strangers, and it can pay dividends to offer early socialization to this breed because it will ensure that the Mastiff is, at least, confident and comfortable when in the company of people it has never met before. Training can be a challenge thanks to the independent nature of this animal. Combined with its sheer size, this means that the American Mastiff may not be considered the most ideal breed for first-time and novice owners.

Are These Dogs Good for Families? 👪

A friendly, loyal, and loving animal, the American Mastiff will form a close bond with all of its family. It does not usually favor one particular person over the rest of the family, and it will get along with family members of all ages.

Its size means that you must be careful when allowing unsupervised time with children because as gentle and understanding as the Mastiff is, it is a huge dog that can accidentally cause serious injury to family members. Although this dog is not known for being outwardly aggressive, it is a very protective animal and will not hesitate to take action if it feels that the family needs its protection.

Does This Breed Get Along with Other Pets?

The breed can also live with other dogs and may live with cats. Again, you have to consider the size of the animal and any other inhabitants of the house, but the Mastiff does not usually have any prey drive so it will not attack other dogs or cats. For the best results, you should always try to introduce a new dog to existing pets when they are all as young as possible. This gives them time to accept one another before they mature.divider-dog paw

Things to Know When Owning an American Mastiff:

The American Mastiff is a large, loyal, and loving dog. It also requires minimal grooming and doesn’t require much exercise. Its size means that this breed does better living in a large property with a garden, rather than an apartment, and you shouldn’t underestimate the impact a 200-pound dog can have on your life.

Food & Diet Requirements 🦴

As you can imagine, the giant Mastiff does have a giant appetite, but this does not mean that you should let yours eat as much as it wants. You should find food that has been made especially for large breed dogs. These have high levels of protein, moderate fat, and low-calorie levels.

The Mastiff can be prone to becoming overweight, so you must monitor what you feed and stick to appropriate guidelines. You will usually find that you need to feed a minimum of 5 cups per day of a good quality kibble. You may choose to give wet food. If you combine dry and wet, ensure that you restrict the amount of each that you give. If you feed half and half, give half the daily dry allowance and half the recommended wet allowance.

You can also feed a raw food diet. It takes more preparation, but it gives you better control of exactly what your dog eats and the level of protein and other nutrients it receives. If you feed treats or use them as a training tool, take these off your dog’s daily allowance.

Try to feed over at least two meals a day. This can prevent your dog from getting bloat and other related digestive complaints.

Exercise 🐕

Although he does not require a huge amount of exercise, the American Mastiff does still have moderate daily needs. Take your giant out once a day, for around half an hour, and this should give ample exercise. You should not expect your Mastiff to run or to walk excessively long distances, and this is one breed that will become very tired very quickly. Too much exercise can cause physical injuries like joint dysplasia.

Training 🎾

Although it is not considered the most intelligent of breeds, the Mastiff is intelligent enough to learn basic training. However, just because it is intelligent enough, doesn’t mean that it can be bothered to do so. The breed is known for being stubborn and if it doesn’t want to learn something, it simply won’t do it. Keep training sessions short, try to make them fun, and don’t expect too much from this breed.

Although there are exceptions, this breed does not usually perform well at agility or canine sports, although it can do well at weight pulling and strength sports.

Image By: ChameleonsEye, Shutterstock

Grooming ✂️

Although the Mastiff is a moderate shedder, it only has a short coat and this makes it easy to groom. Brush weekly to remove dead hairs and to prevent as much fur from making it onto the floor and the sofa. Fortunately, the Mastiff will usually appreciate the attention and it presents a good opportunity for you both to bond.

Check ears regularly. Look for signs of wax buildup or a smell that might indicate there is some kind of infection, and use a damp cloth to clean out any excess mess.

Cut your giant’s nails every 1-2 months, as required, and try to get him used to having his teeth brushed daily or every other day by starting when he is still a puppy. This will make it easier in the long run and help ensure that you can get your hand a toothbrush in its mouth when it’s older.

Health and Conditions 🏥

The breed is considered generally healthy, but its size does mean that the Mastiff is prone to some musculoskeletal and respiratory problems. Hip dysplasia is the most common complaint in dogs of this size and occurs when the thigh doesn’t fit precisely into the hip joint.

You may never know that a dog suffers from this condition, but some dogs will experience considerable pain and show signs of lameness as a result. Although the parents should have been screened for this condition, even a successful screening program cannot completely prevent you from getting a dog that suffers from hip dysplasia.

Serious Conditions:
  • Joint dysplasia
Minor Conditions:
  • Eye problems
  • Hyperthyroidism
  • Lameness
  • Skin problems


Male vs Female

Females usually weigh between 140 and 180 pounds, and it is the male Mastiff that averages between 150 and 200 pounds, so the male is likely to be a little bigger than the female. Other than this, there are some anecdotal reports of males being more territorial and females being more protective of family members, but this is by no means guaranteed.

3 Little-Known Facts About the American Mastiff

1. Mastiffs Are Ancient Breeds

Mastiffs are described as being ancient dogs and it is believed that they originated with Alaunt and Molosser dogs. There are records of this ancient breed being used to chase lions thousands of years ago. The American Mastiff is a much more recent addition to the list of breeds. It was developed over 20 years ago and first recognized by the Continental Kennel Club in 2000. It is descended from the English Mastiff, and in most English-speaking countries, the term Mastiff is used to refer to the Old English Mastiff breed and not the American Mastiff.

Ancient breeds were used for hunting a wide range of animals. They were also used to protect livestock and act as guardians and would have been employed as formidable war dogs.

2. The American Mastiff Is a Giant Breed

Mastiffs of various kinds are among the biggest breeds in the world. The American Mastiff is described as being as tall as 36 inches and weighing as much as 200 pounds. In 1989, an American Mastiff named Zorba was registered as the largest dog in the world. He was 37 inches tall at the shoulder and weighed a staggering 343 pounds.

Although your Mastiff is unlikely to reach quite this size, it will be a giant of a dog, and it is no minor undertaking to adopt such a huge animal. A dog of this stature will take over your sofa, your house, and your time.

3. They Reach Maturity Late

The American Mastiff has a life expectancy of around 12 years, which is shorter than a lot of breeds but typical for giant breeds like this. Despite this, the Mastiff will only reach full maturity and stop growing at the age of about 3. Until this time, it is still considered a puppy and then an adolescent dog.

Most vets and nutritionists agree that a puppy American Mastiff should be given adult dog food because of its size and how much protein it requires. Young Mastiffs are susceptible to joint injuries. Light play and general exercise are fine, but jumping over obstacles or taking part in obstacle courses should be avoided. In fact, most owners do not let their Mastiffs upstairs because they can struggle to safely navigate their way back down the stairs and can get injured in the fall.

Image By: PJW31189, Shutterstock


Final Thoughts

The American Mastiff is a giant breed of dog and can weigh as much as 200 pounds, growing to a height of 36 inches. The loyal and loving dog will benefit from a moderate exercise plan, but should not have too much exercise or exercise that is too hard. A relatively short walk each day should be enough.

The breed will get along very well with its family and can be quite protective. While reasonably intelligent and capable of learning basic training, the breed is known for being independent, stubborn, and sometimes a bit lazy, so it can be difficult to train. For this reason, the Mastiff is considered a good breed for experienced owners, rather than novice and first-time dog handlers.

Your Mastiff will eat a lot and you need to ensure that it does not eat more than a reasonable daily amount, although even a reasonable amount will usually mean five cups of kibble a day. Look for signs of musculoskeletal illnesses and conditions like joint dysplasia, and respiratory problems, because these are the most common conditions in this breed.

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Featured Image Credit: Peakpx

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