English Mastiff Mixed With Saint Bernard: Giant Breed

When you cross two of the largest dog breeds on the planet, you get a companion that commands attention in every room — and every doorway. The English Mastiff mixed with Saint Bernard (sometimes called a Saint Mastiff or Mastiff Saint) is a giant designer cross that combines the Mastiff's calm guardian instincts with the Saint Bernard's gentle, rescue-dog heritage. This is not a dog for the faint of heart, the small of home, or the thin of wallet.

I've worked with owners of giant breeds for years, and this particular mix sits at the extreme end of the size spectrum. Before you bring home a puppy that will outweigh most adults in your household within 18 months, you need a clear picture of what you're signing up for — the predictable traits, the genetic gamble, and the real costs involved.

The Parent Breeds: What Goes Into This Mix

Understanding the parent breeds is the single most useful thing you can do when evaluating any designer cross. Each parent contributes a pool of traits, and your individual dog will draw from both — sometimes in unexpected combinations. Here's how the English Mastiff and Saint Bernard stack up side by side.

The English Mastiff is recognized by the AKC as one of the heaviest breeds in existence, with males regularly exceeding 200 lb (91 kg). They were historically bred to guard English estates and are known for their quiet, watchful demeanor — they tend to position themselves between their family and strangers rather than bark aggressively.

The Saint Bernard originated in the Swiss Alps, where monks at the Great St. Bernard Hospice used them for rescue work in treacherous mountain passes. They carry a more overtly friendly, sociable temperament compared to the Mastiff's reserved nature, and they tend to be more physically expressive — think enthusiastic tail wagging and full-body lean-ins.

How Big Will an English Mastiff Mixed With Saint Bernard Get?

This is where we need to set realistic expectations. Because both parent breeds are giants, the size range for this mix is enormous — and it's genuinely difficult to predict where an individual puppy will land until they're at least 6 months old.

A few things to understand about giant breed growth:

• Growth plates close late. Giant breeds don't finish skeletal growth until 18–24 months. Pushing high-calorie diets to accelerate growth increases the risk of developmental orthopedic diseases like hip dysplasia and osteochondrosis.
• Puppy weight at 8 weeks is a rough indicator. A Mastiff-Saint Bernard puppy weighing 18–22 lb (8–10 kg) at 8 weeks is likely tracking toward the upper end of the range.
• Sex makes a major difference. Males can be 30–50 lb (14–23 kg) heavier than females in this mix.

For context, you'll need a vehicle that can accommodate a 200-lb dog for vet visits, a bed frame that won't collapse, and doorways wide enough for a dog that's nearly 3 feet long from nose to tail base.

Generations and Genetics: F1, F1B, and Beyond

Here's an important reality check: unlike Poodle mixes (Labradoodles, Goldendoodles) where breeders have established multigen lines over decades, the Mastiff-Saint Bernard cross is relatively uncommon. Most puppies you'll find are F1 — first-generation crosses from two purebred parents. This means:

• Trait predictability is low. You cannot reliably predict coat type, exact adult size, or precise temperament from an F1 litter.
• Health testing of both parents is critical. Because there's no established breeding program smoothing out genetic risks, you're relying entirely on the health clearances of the individual parents.
• "Multigen" claims should be scrutinized. Ask for pedigree documentation. Many breeders use the term loosely.

Temperament: What to Expect (and What Might Surprise You)

Both parent breeds fall into the "gentle giant" category, which is encouraging — but temperament inheritance in crossbreeds is not a simple averaging of the parents. Your dog may lean heavily toward one breed's personality or present a blend that shifts as they mature.

Best-Case Temperament Profile

A well-socialized Mastiff-Saint Bernard mix typically displays:

• Calm indoor demeanor — these dogs are notorious couch potatoes who take up an entire sofa
• Strong family bonding — they tend to form deep attachments and follow their people room to room
• Gentle with children — both breeds have reputations for patience, though no giant dog should be left unsupervised with small children due to accidental knocking over
• Moderate alertness — they'll notice strangers and may position themselves protectively, but typically without aggressive displays
• Low exercise drive — 30–45 minutes of daily walking is usually sufficient, making them surprisingly manageable despite their size

Challenging Scenarios to Prepare For

• Stubbornness during training. The Mastiff side can contribute a "what's in it for me?" attitude. Force-free, positive reinforcement methods are essential — these dogs shut down under harsh correction, and their size makes any aversive technique both ineffective and dangerous.
• Drooling. Both breeds are prolific droolers. Expect to wipe down walls, furniture, and your own clothing regularly. Keep drool towels in every room.
• Separation distress. Both breeds bond intensely. Dogs left alone for 8+ hours daily are at high risk for destructive behavior and anxiety. This mix needs a household where someone is home for significant portions of the day.
• Delayed maturity. Giant breeds often retain puppy-like behavior and clumsiness until 2–3 years old. You'll have a very large dog acting like an adolescent for longer than most breeds.
• Same-sex dog aggression. Some Mastiff lines show dog aggression, particularly male-to-male. Early socialization is non-negotiable, and introductions to new dogs should always be managed carefully.

Trait Variability Chart

Coat, Grooming, and the Shedding Reality

Is this mix hypoallergenic or low-shedding? No. Neither parent breed carries the low-shedding gene, and this cross will shed moderately year-round with heavier seasonal shedding (typically spring and fall). If you or a household member has dog allergies, this is not the right mix for your home.

Coat Possibilities

• Short coat (Mastiff-inherited): Dense, straight, close-lying hair. Easier to maintain but still sheds consistently. Most common outcome in F1 crosses.
• Medium-long coat (Saint Bernard-inherited): Slightly wavy, longer around the neck, chest, and tail. Requires more frequent brushing to prevent matting behind the ears and on the hindquarters.
• Undercoat: Both breeds have double coats, so expect a dense undercoat regardless of outer coat length. During shedding season, you'll pull out tufts of undercoat that could stuff a pillow.

Grooming Routine

Professional grooming for a dog this size is expensive and logistically challenging — many grooming salons have weight limits or charge premium rates for giant breeds. Plan to do most grooming at home and invest in a raised grooming table (rated for 220+ lb) if you can accommodate one.

Health Considerations: The Hybrid Vigor Myth vs. Reality

Let's address this directly: hybrid vigor does not eliminate health risks in giant breed crosses. The concept of heterosis (hybrid vigor) applies when two genetically distant populations are crossed, potentially reducing the expression of recessive disorders. However, the English Mastiff and Saint Bernard share significant genetic overlap — both are giant working breeds with similar body conformations and overlapping predispositions. According to the Merck Veterinary Manual, many orthopedic and cardiac conditions common to giant breeds have polygenic inheritance patterns that crossbreeding does not reliably mitigate.

Here are the specific health conditions this mix may inherit from either or both parent breeds:

Preventive Health Protocol

Responsible ownership of this mix requires a proactive veterinary partnership. Here's a recommended screening schedule:

• 4–6 months: Baseline orthopedic exam; elbow and hip radiographs if lameness is noted
• 12 months: OFA or PennHIP hip evaluation; elbow evaluation; cardiac exam
• 24 months: Full OFA hip/elbow certification radiographs; echocardiogram baseline
• Annually after age 4: Cardiac exam with auscultation; thyroid panel; joint mobility assessment
• Age 6+: Biannual veterinary visits; cardiac ultrasound if any murmur detected; cancer screening (thoracic radiographs, abdominal ultrasound)

Always consult your veterinarian to tailor this screening schedule to your individual dog's needs. Pet insurance is strongly recommended — giant breed veterinary costs are among the highest of any dog category, and a single emergency surgery can exceed $7,000.

Cost Breakdown: Purchase Price and Lifetime Ownership

This is where many prospective owners experience sticker shock. Giant breeds are expensive at every stage — from purchase to daily feeding to end-of-life care.

Puppy Purchase Price

Check ASPCA adoption resources and Mastiff or Saint Bernard breed-specific rescues (Mastiff Rescue Network, Saint Bernard Rescue Foundation) — mixed-breed dogs from these parents do occasionally end up in rescue when owners underestimate the size and cost of care.

First-Year Estimated Costs

Annual ongoing costs after the first year typically run $2,500–$5,000, depending on food quality, veterinary needs, and whether any chronic conditions develop. End-of-life care for a giant breed — including potential hospice, mobility support, and humane euthanasia with aftercare — can add $1,000–$3,000 in the final year.

Training and Exercise: Managing a Gentle Giant

Training a 180-lb dog is fundamentally different from training a 30-lb dog. The margin for error is smaller because an untrained giant dog can pull an adult off their feet, knock over children, or become impossible to manage on a leash.

Exercise Requirements

• Daily walking: 30–45 minutes, split into two walks if possible. Avoid forced running or high-impact exercise until growth plates close (18–24 months).
• Mental stimulation: Puzzle feeders, scent work, and gentle trick training keep their minds engaged without stressing joints.
• Heat sensitivity: Both breeds are brachycephalic-adjacent (the Mastiff has a shortened muzzle) and prone to heat stress. Exercise in temperatures above 80°F (27°C) should be limited to early morning or evening, with constant access to water and shade.

Training Priorities

Focus on these skills before your puppy reaches 6 months and 80+ lb:

1. Loose-leash walking — use a front-clip harness (e.g., Ruffwear Front Range in XL/XXL) from day one. A 200-lb dog pulling on a leash is dangerous for both of you.
2. "Drop it" and "leave it" — giant dogs can ingest dangerous objects before you can physically intervene.
3. Polite greeting (four on the floor) — a jumping Mastiff mix can injure people.
4. Settle/mat training — teach a default "go to your bed and lie down" behavior for when guests visit or you need your dog stationary.
5. Cooperative care — train your dog to voluntarily present paws for nail trimming, accept ear handling, and stand for veterinary exams. This is not optional for a dog this size.

All training should use positive reinforcement methods — food rewards, praise, and play. The American Veterinary Society of Animal Behavior (AVSAB) recommends against aversive training tools including shock collars, prong collars, and physical corrections, which can damage your dog's trust and potentially trigger defensive aggression in a dog powerful enough to cause serious harm.

Who Should (and Shouldn't) Get This Mix

After covering size, health, temperament, and cost, here's a decision framework to help you evaluate fit.

Frequently Asked Questions

What two breeds make up the English Mastiff mixed with Saint Bernard?

This designer cross combines the English Mastiff (a British estate guardian breed dating back over 2,000 years) with the Saint Bernard (a Swiss Alpine rescue breed developed by monks at the Great St. Bernard Hospice). Both belong to the AKC Working Group and share giant-breed body types, double coats, and calm temperaments.

How big will this mixed breed get?

Adult males typically weigh 160–195 lb (73–88 kg) and stand 27–30 inches (69–76 cm) at the shoulder, though some can exceed 220 lb (100 kg). Females generally weigh 130–155 lb (59–70 kg). Full physical maturity — including body mass filling out — can take up to 3 years.

What will the temperament be like?

Most individuals are calm, loyal, and gentle with family members. Expect a range from Mastiff-like reserve with strangers to Saint Bernard-like friendliness. Early socialization (starting before 16 weeks) is essential for a well-adjusted adult. Both parent breeds bond intensely with their families and do poorly with long daily absences.

Is this mix hypoallergenic or low-shedding?

No. Both the English Mastiff and Saint Bernard have double coats that shed moderately year-round and heavily during seasonal coat blows. This mix will produce significant dander and is not suitable for allergy sufferers. There is no such thing as a truly hypoallergenic dog, but this cross is among the heavier shedders.

What health issues might this mix inherit?

The most significant concerns are hip dysplasia, elbow dysplasia, dilated cardiomyopathy, gastric dilatation-volvulus (bloat), entropion/ectropion, osteosarcoma, and cruciate ligament rupture. Hybrid vigor does not eliminate these risks because both parent breeds share similar giant-breed predispositions. Health screening of both parents (OFA hips, elbows, cardiac) is essential before breeding.

How much does this designer mix cost?

Puppies from reputable breeders with health-tested parents typically cost $1,200–$3,000. First-year total ownership costs (including veterinary care, food, supplies, and insurance) range from $4,400 to $9,800. Annual ongoing costs are $2,500–$5,000. Adoption through breed-specific rescues costs $200–$600 but availability is limited.

Can this mix live in an apartment?

While both parent breeds are relatively low-energy indoors, the sheer physical size of this mix makes apartment living impractical in most cases. You'll need wide doorways, ground-floor or elevator access, nearby outdoor space for bathroom breaks and walks, and a landlord or HOA that permits dogs over 100 lb — many rental properties enforce breed or weight restrictions.

How long do English Mastiff and Saint Bernard mixes live?

Expect a lifespan of 7–10 years, consistent with giant breed averages. Some individuals may live to 11 or 12 years with excellent genetics and proactive veterinary care, but this is the exception rather than the norm. Cancer (particularly osteosarcoma) and cardiac disease are the leading causes of premature death in giant breeds.