American Mastiff

140-180 lbs
United States
AM Mastiff

The American Mastiff can only be described as a giant of a dog. This colossus canine grows to reach almost 200 pounds and can stand up to 36 inches tall. That is a lot of dog, but luckily, they have a mellow temperament and are not aggressive. They can be stubborn and like to have their own way, so they do need an experienced dog handler to raise them to achieve their best. A strong leader with a lot of patience is the best owner for this dog, otherwise, they can tend to take over and become demanding. But they have a heart of gold and adore their family. They are kind and gentle with children, showing patience and tolerance to their antics. As with all dogs, this one needs socializing at an early age to encourage positive interaction with strangers and other dogs. The American Mastiff has a dryer mouth than the English Mastiff, which means less drool - but not no drool. A huge dog means they do need a house or apartment that has that extra space for them, but luckily they are quite a couch potato and are relatively inactive inside and rarely bark. They make wonderful companions and great watchdogs.

purpose Purpose
Working, Companion
history Date of Origin
ancestry Ancestry
English Mastiff, Anatolian Mastiff

American Mastiff Health

Average Size
Male American Mastiff size stats
Height: 28-36 inches Weight: 160-200 lbs
Female American Mastiff size stats
Height: 26-34 inches Weight: 140-180 lbs
Major Concerns
  • Joint Dysplasia
Minor Concerns
  • Skin Problems
  • Foreleg Lameness
  • Eye Problems
  • Hyperthyroidism
Occasional Diagnoses
  • Bloat
Occasional Tests
  • Eye Examinations
  • Serum Chemistry
  • Regular Full Physical Examination By Veterinarian
  • Full Blood Work
  • Blood Chemistry
  • Diagnostic Imaging
  • Skin Scrapings and Biopsies

American Mastiff Breed History

The American Mastiff is a relatively new breed although the Mastiff dogs have been around for centuries. Originally they were bred as an English war dog, where they had the job of attacking the enemy soldiers. Ferocious and tenacious - they were a dog to be feared. Between wars, they guarded the rich and wealthy homesteads and were occasionally trained in the sport of bear baiting. Thankfully in recent years, the aggression has been bred out of the dog, and they mellowed into a gentle giant. Mastiffs came to America with their colonist owners on the ship the Mayflower and were used as protection for families, stock and property. Sadly, there were a lot of inbreeding issues which began to cause health complications and a breeder called Fredericka Wagner in Piketon, Ohio decided to breed a new Mastiff to overcome these problems. She began in the late 1980s and carefully combined the Anatolian dog with the Mastiff. The offspring was vigilantly regulated with who they were bred with and eventually Fredericka developed the dog that had a tighter lip line. The dog she named the American Mastiff had a drier mouth and drooled less than the parent Mastiffs. By the late 1990s, Wagner had stopped outcrossing and was breeding with her existing dog lines. Later in 2002, Wagner started allowing a few breeders to join her newly formed American Mastiff Breeders Council. This has widened the gene pool to just 11 breeder members and they work hard to ensure the health and temperament of their dogs. Debate still rages as to whether the American Mastiff is as good as the breeders claim, but the fact remains that they have achieved a gentle giant of a dog that so far excels in health and temperament.

American Mastiff Breed Appearance

The American Mastiff is a giant sized dog who can weigh in at up to 200 pounds. While they look similar to their English counterparts, they are much slimmer than the English Mastiff and have a longer muzzle, fewer wrinkles and seem to have a kinder expression. They have a solid rectangular head, floppy high set ears,  and they have a drier mouth (less drooling) and a black nose. The body of this imposing canine is massive and is solid muscle, although they still have that athletic look to them. Their neck is thick with a slight arch that blends into the deep chest. A long straight back and solid powerful legs are completed with a set of massive padded paws. They have a long, muscular whip-like tail. This breed comes in colors such as fawn, brindle, and apricot and can vary in tone, as well as have complimentary white markings and a black mask that gives them a mysterious, almost forbidding look at first glance. That is until you see their warm brown eyes that twinkle with humor.

Eye Color Possibilities
brown American Mastiff eyes
amber American Mastiff eyes
Nose Color Possibilities
black American Mastiff nose
Coat Color Possibilities
fawn American Mastiff coat
brown American Mastiff coat
brindle American Mastiff coat
Coat Length
Short Medium Long
Coat Density
coat density
Sparse Normal Dense
Coat Texture
coat texture
American Mastiff straight coat texture
Straight Wiry Wavy Curly Corded

American Mastiff Breed Maintenance

Usually, you can get away with a brushing once a week, but if your dog is in a heavy shedding phase, you will need to raise the brushing sessions up to twice per week at least. The American Mastiff rarely needs bathing but it is a good practice to rub them down every second week with a damp cloth just to keep them smelling sweet. Although the coat is short and straight, the sheer size of this dog means it will take some time to complete their grooming. Grooming time won't worry your massive companion as they love your attention and crave your interaction. It is advisable to train your dog when they are still small to get used to having their teeth brushed almost daily, and to have their ears examined, and toenails trimmed. If you leave it to later, your gentle giant may push you away and refuse to cooperate. This large dog requires their mouth to be wiped after eating and drinking to avoid any drooling.

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Brushes for American Mastiff
Pin Brush
Pin Brush
Slicker Brush
Slicker Brush
Nail Clipper
Nail Clipper
Brushing Frequency
fur daily fur weekly fur monthly
American Mastiff requires weekly brushing
Daily Weekly Monthly

American Mastiff Temperament

While the sheer size of this amicable canine can look daunting to a visitor, they are not an aggressive dog unless you or a family member are threatened. Then beware, as they will defend their family with outstanding courage and determination. The American Mastiff is a quiet, dignified dog who is totally loyal and devoted you; they are kind and gentle and can even tend towards being 'clingy'. They love being with their family and pine when they are left alone. They do have some habits that may take some adjusting to, such as flatulence, snoring, shedding hair and some slobber. Dignified they may be, but they are not refined! They can be wary in the presence of strangers, but once they get to know someone, they warm up to their usual friendly selves. They make a good watch dog as they will alert you to intruders. They can be stubborn to train, as they like to do things their own way and may rebuff your methods. Patience and kindness are needed; yelling or losing your cool will not achieve anything with this dog. Instead, make the training fun. Have fewer repetitions to prevent boredom, and incorporate challenges that stimulate their mental abilities to get them to think more about how to solve something. They love children and are patient and kind to them, but always supervise a young dog as their size can cause unintended injury to little ones.

American Mastiff Activity Requirements

The American Mastiff does need a certain level of exercise to keep them healthy and happy, although they can tend to be lazier as they mature. A daily walk or two is ideal, they will happily amble alongside you and drink in the sights. Walking is a great opportunity to socialize your dog and get them used to meeting other people and other dogs. Forget long runs or cycling with this dog, as their size cannot maintain a fast pace for long. They need to be challenged mentally as well as physically. If either is lacking, this pup can become nervous, destructive and generally hard to live with as they can become stubborn and disobedient. Although they are very intelligent, they can be hard to train as they want to do things their way. Ensure the training is not too repetitive or they will lose focus and get bored, which means they won't obey when you want them to. They require a strong leader/owner who is consistent with their training and adheres to their own rules. This impressive pooch is best for the experienced dog handler who is used to managing a massive dog.

Activity Level
low activity medium activity high activity
Low Medium High
Rec. Walk Mileage Per Week
10 miles
walk mileage
Minutes of Activity Per Day
60 minutes
activity minutes

American Mastiff Food Consumption

Cups Per Day
4 cups
cup per day cost cup per day cost cup per day cost cup per day cost
Daily Cost
$2.75 - $3.00
food bowls daily cost
Monthly Cost
$80.00 - $90.00
food bag monthly cost

American Mastiff Height & Weight

6 Months
Male American Mastiff size stats at six months
Height: 15.0 inches Weight: 55.0 lbs
Female American Mastiff size stats at six months
Height: 13.0 inches Weight: 49.5 lbs
12 Months
Male American Mastiff size stats at 12 months
Height: 25.0 inches Weight: 110.0 lbs
Female American Mastiff size stats at 12 months
Height: 23.0 inches Weight: 105.0 lbs
18 Months
Male American Mastiff size stats at 18 months
Height: 33.0 inches Weight: 180.0 lbs
Female American Mastiff size stats at 18 months
Height: 30.0 inches Weight: 160.0 lbs

American Mastiff Owner Experiences

8 Weeks
3 People
House & Yard
Walking to the park letting her run around
So far its been a great experience. Dasiy is my first America Mastiff 8week old she’s a chocolate Merle so beautiful
2 years, 1 month ago
1 Year
5 People
House & Yard
very loyal,brave,lazy,naughty and playful
2 years, 6 months ago
7 Years
2 People
House & Yard
Walking our 2.5 acres and playing with our GSD
We had an English Mastiff for 13.5 years. We also fostered a Mastiff for the local Mastiff Rescue. We whelped 6 Mastiff puppies. Liberty is our first American Mastiff.
2 years, 8 months ago
5 Years
2 People
House & Yard
Couch potato, periodic play in the yard.
After having shared the house with an English Mastiff, the American Mastiff compares favourably. Affectionate wary of strangers, well mannered if you exclude the farting, snoring, and velcro adhesion. Follows me everywhere in the house. Lovely brindle companion. Good with cat and other in house dog. We love her.
3 years, 6 months ago
23 Months
2 People
House & Yard
I owned a 194 Presa many years ago and wanted another giant breed. Pancho lives with a minature dachshund and a cat. I picked up Pancho from Fredericka the creator of this breed 23 months ago. We flew to Ohio and picked up then drove 12 hours back to FL so he would wake up at the beach where I live. I have found pancho o be a very smart boy who listens to most commands. Regarding dryer mouth …. I don’t perceive of this at all! We have slobber towels around the house and anytime he drinks we make sure we are there to dry his mouth. Size… according to the breeder she noted that pancho will probably be 220+ pounds when full grown. He currently stands around 36” tall thus anything on a counter is within eyesight and his mouth. Food I had him on Orijen large breed puppy for 19 months ….currently transition over to royal canin giant breed Kimble— note this Kimble is huge! Synopsis I love having another giant breed dog Advice - if you get a dog this size plan on all meds being triple in cost. Make sure you also get dog insurance you will need it eventually. Love the American Mastiff.
2 years, 9 months ago
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