Are Bullmastiffs Aggressive Dogs?

The Bullmastiff is a superb guard dog, but does this mean that they’re aggressive? To answer this question, let’s learn more about the nature of this powerful breed.

Mar 17, 2024byLisa Szymanski
are bullmastiffs aggressive dogs

Most Bullmastiff owners will tell you that their dogs are protective and alert, but they wouldn’t ever describe them as dangerous. As with any breed, without training and getting them socialized, there’s always the possibility of aggression. But in a 120 lb Bullmastiff, an aggressive reaction could spell disaster. The Bullmastiff is a guard dog, which means that they have a strong protective instinct. It’s this protectiveness that many people fear. To better understand whether Bullmastiffs are aggressive dogs, we need to learn more about their history and true nature.

The History of Bullmastiffs

historic image of the bullmastiff
The Bullmastiff breed dates back to the 1860s.

The Bullmastiff is an incredibly strong dog that was bred in the mid-1800s in England. Their job was to protect game against poachers, which earned them the nickname of the Gamekeeper’s Night Dog. To keep intruders at bay, these dogs had to be alert, which meant acting as soon as they detected a threat. Their breeding includes the bulldog, which was considered far too fierce to protect farms, and the traditional mastiff, which wasn’t fast enough to chase poachers.

Despite their drive to guard property, animals, and people, these dogs had to obey their handlers at all costs. When trained, the Bullmastiff proved to be a highly dependable dog that was energetic and powerful yet attentive and devoted to their owners. They were only recognized by the American Kennel Club in 1993, but since then, they have made their mark as brave and intelligent dogs.

Temperament and Personality: Are Bullmastiffs Very Protective?

alert bullmastiff standing near fence
Alert and on guard.

A lot of big dogs are misunderstood, and the Bullmastiff is one of them. Don’t get me wrong, Bullmastiffs are powerful dogs with a very intimidating appearance, but deep down, they aren’t vicious dogs that are waiting to attack. The true temperament of a mastiff is described as loyal and loving toward their family. They’re willing to please, and with firm leadership, these intelligent canines will quickly respond to commands through regular training.

You can’t talk about the mastiff personality without discussing their protectiveness, and this is where the breed has earned its fearful reputation. A Bullmastiff has a natural drive to protect the people they know and love. But if this part of their personality is not managed with training and socialization, it can turn into aggression. A giant dog that feels the need to take over and protect will charge and possibly bite people and other animals without warning. Although the Bullmastiff wasn’t bred to maul intruders, they were vigorously trained to follow strict commands. Today, much of the aggression that you see in mastiffs and many other bully breeds is attributed to the absence of training from a young age.

How Dangerous is a Bullmastiff?

bullmastiff running with tongue out
The Bullmastiff is a fast and quick-witted dog.

Bullmastiffs with the correct leadership and boundaries in their home are gentle and lovable dogs. But, this isn’t true for every mastiff. Unfortunately, a major determinant of their temperament is genetic. When you choose a Bullmastiff puppy, you want to know that the parents have been picked for their superb nature. Mastiff owners will tell you that they paid careful attention to the personalities of the dogs in the breeding program before selecting a puppy. This means that breeders put effort and time into upholding the original temperament of the Bullmastiff, which wasn’t one of ferociousness.

The question is whether a Bullmastiff is a really dangerous dog. Well, a powerful dog with a strong protective nature can be extremely dangerous if not properly trained. Much like a German shepherd or a pitbull, if you don’t socialize them, these dogs can develop fear and anxiety, which are terrible traits. A fearful or anxious dog is a reactive one, and when you add power and determination, that’s when you get unwanted aggression.

Can Bullmastiffs Make Good Pets?

bullmastiff standing in yard
These giant dogs are good at learning commands.

Bullmastiffs can make excellent pets, but I wouldn’t recommend them if you’re a first-time dog owner or have very small kids. That’s because, throughout the lives of these massive canine companions, you must consistently stick to rules and training. If you don’t have experience with big protective dogs, you might find it challenging to keep your Bullmastiff under control. In the case of children, very young kids might tug on the dog or try to climb on top of them, which is a problem. The dog might react to pain and irritation, and trying to “ride” the mastiff also creates stress and discomfort. Young children should always be monitored around any large dog breed and taught how to handle these animals with care and respect.

Training a Bullmastiff: What You Should Know

two bullmastiff puppies on grass with dog toys
Training should start when they’re puppies.

Giving your Bullmastiff the best possible start means investing in training. This doesn’t mean that you have to be a drill sergeant all the time, but firm and consistent leadership is crucial when raising protective dogs. I speak from experience as my adult Boerboel, which is related to the mastiff, goes into guard dog mode around strangers and unfamiliar pets. While it’s a commitment, you can make training fun by introducing different dog toys and games. Gradually introduce puppies to other people and animals and correct behaviors such as growling or jumping.

The most important part of training a Bullmastiff is getting them to walk well on lead. As puppies, they might be easy to handle, but if a dog weighing 130 lbs refuses to go to the vet, it’s not fun. Teach them not to pull or react to other dogs while walking or at the dog park. You can introduce commands such as heel and stay and reinforce them with a treat or praise. Be consistent with training, and you’ll raise a confident and friendly dog.

Is a Bullmastiff Aggressive? Here’s the Verdict

close up of bullmastiff face
A big dog with a big heart.

Any dog, particularly the guard dog breed, can become aggressive. Looking at the Bullmastiff, these dogs don’t have a history of aggression. When they were trained to target poachers, they were not meant to maul the intruder but to pin them until their handler arrived. These mastiffs are not meant to be aggressive, but if you don’t train them or create positive experiences, their protectiveness takes over. Showing teeth, growling, and lunging are aggressive behaviors. The heart of the Bullmastiff is one of loyalty, courage, and devotion. With the right approach and a pack leader mindset, you can raise an incredible dog that will defend you when you need them to.

Lisa Szymanski
byLisa Szymanski

Lisa is a wildlife enthusiast who enjoys hiking and gardening and has four years of experience volunteering at pet shelters. She is the proud mom of two dogs, a Pitbull named Ragnar, a Boerboel named Blueberry, and four feisty chickens, or as she calls them, the \"queens of the yard,\" Goldie, Gray, Peaches, and Brownie.