Sometimes thought to be aggressive and dangerous, the American Mastiff is in fact a loving, kind-natured, large dog breed. With the right training, you'll see that they are affectionate, gentle giants. And great with children!

Origins of the American Mastiff

The American Mastiff looks pretty much identical to the English Mastiff in colour, shape and size. The breed was developed by Fredericka Wagner of Piketon, Ohio and is primarily descended from the English Mastiff, often known simply as the Mastiff.

The goal of this dog breed was to develop a dog that had the size, temperament, disposition, and the appearance of the Mastiff, but with fewer health problems, and a much dryer mouth than other mastiff breeds.

The Continental Kennel Club recognised the breed in 2000 and was the first organisation to do so. As of yet, the American Mastiff is not recognised by either the American Kennel Club or the United Kennel Club.

Physical characteristics

As said above, the American Mastiff resembles the English Mastiff. They can be easily recognised by their robust appearance and bulging muscles. They are powerful dogs with a broad head, dropped ears and wide-set eyes of a brown/amber colour.

Their fur is short, dense and comes in different varieties of colours (apricot, fawn and brindle). American Mastiff puppies are born with a dark fur but this lightens as they grow older.

As an adult, their height is typically 32-39 inches for males and they can weigh from 160 pounds to over 200 pounds. The height for adult females ranges from 28-34 inches and average 140-180 pounds.


It has been claimed that American Mastiffs have longer life expectancies than other giant breeds (around 8 to 11 years).

That being said, like a lot of big dog breeds, they can suffer from skeletal growth abnormalities. Their bones can grow much faster than those of smaller dog breeds. Check with your vet to see what diet you should give your pup. If given the wrong diet, their bones can develop improperly.

This dog breed needs a lot of exercise, and will enjoy long walks or any other activity that lets them use up their energy. Properly exercised American Mastiffs can often be very lazy and laid back at home. In fact, many owners of this breed describe their dogs as committed, "couch potatoes".

Their exercise must be monitored carefully, as too much or certain types of exercise can cause problems e.g. the breed shouldn't jump greater than a certain height due to their joints.


American Mastiffs are friendly giants. Well trained, they can be calm, controlled and confident. They are understanding, patient and loving towards their family and children. However, as puppies, they may not be the best housemates for small children as they can get excited and accidentally push a child over when trying to play.

They are not aggressive by nature but make excellent guard dogs and enjoy being the protector of their family. Loyalty is equally distributed amongst family members, including to children with which they are patient and gentle.

Here's to breaking old myths!

What do you love most about the American Mastiff?

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