English Mastiff and St. Bernard Mix: The Complete Breed Guide
Everything about the English Mastiff and St. Bernard mix: size, temperament, health risks, grooming needs, cost.
If you've been researching giant breed dogs, you've likely come across the English Mastiff and St. Bernard mix — sometimes called the Saint Mastiff or Mastiff Bernard. This is one of the largest designer crosses in existence, combining two of the heaviest breeds on the planet into a single dog that can tip the scales well past 200 pounds.
But before you fall in love with the idea of a gentle giant lounging on your couch (which will need reinforcing), there's a lot to understand about what this crossbreed actually looks like in practice. Unlike purebred dogs with predictable breed standards, mixed breeds carry inherent variability — and when both parent breeds are this massive, that variability has real-world consequences for your home, your budget, and your dog's health.
This guide covers everything prospective owners need to know, drawn from breed standards, veterinary literature on giant breed health, and practical experience with large-breed households.
The Parent Breeds: English Mastiff vs. St. Bernard
Understanding any mixed breed starts with understanding its parents. Both the English Mastiff and the St. Bernard are ancient, massive breeds — but they developed for very different purposes and carry different genetic profiles.
| Trait | English Mastiff | St. Bernard |
|---|---|---|
| AKC Group | Working | Working |
| Weight Range | 120–230 lb (54–104 kg) | 120–180 lb (54–82 kg) |
| Height at Shoulder | 27.5–30+ in (70–76+ cm) | 26–30 in (66–76 cm) |
| Coat Type | Short, dense, smooth | Short-hair or long-hair variety |
| Origin | England — guarding, war dogs | Swiss Alps — rescue, draft work |
| Temperament | Calm, courageous, docile | Playful, gentle, inquisitive |
| Typical Lifespan | 6–10 years | 8–10 years |
| Drooling Level | Moderate to high | High (especially after drinking) |
| Energy Level | Low to moderate | Moderate |
The English Mastiff, recognized by the AKC, holds records as one of the heaviest dog breeds ever documented. Males routinely exceed 200 lb (91 kg). They were historically used as estate guardians in England and have a deeply ingrained protective instinct paired with remarkable calm indoors.
The St. Bernard originated in the Swiss Alps, where monks at the Great St. Bernard Hospice bred them for rescue work in mountain passes. They tend to be slightly more active and playful than Mastiffs, with a stronger retrieving drive and a well-documented love of snow and cold weather.
How Big Will an English Mastiff and St. Bernard Mix Get?
This is the question everyone asks, and the honest answer is: very, very large. But the specific numbers vary considerably between individual dogs.
| Measurement | Minimum Expected | Maximum Expected |
|---|---|---|
| Adult Weight (Male) | 150 lb (68 kg) | 250+ lb (113+ kg) |
| Adult Weight (Female) | 120 lb (54 kg) | 190 lb (86 kg) |
| Height at Shoulder | 26 in (66 cm) | 32+ in (81+ cm) |
| Time to Full Size | 18 months | 3 years (skeletal maturity) |
Giant breeds grow slowly. Your English Mastiff and St. Bernard mix puppy won't reach full skeletal maturity until 24–36 months. During that growth period, managing nutrition carefully is essential — overfeeding a giant breed puppy accelerates growth rate and dramatically increases the risk of developmental orthopedic diseases like osteochondrosis and hip dysplasia.
A practical note: plan for a dog that will weigh at least 160 lb (73 kg). If your living situation, vehicle, or budget can't accommodate that minimum, this mix isn't the right fit regardless of where on the spectrum your individual dog lands.
Temperament: What to Expect from This Cross
Both parent breeds are known for gentle, patient temperaments — which is good news. But "gentle giant" doesn't tell the full story.
Best-Case Temperament Scenario
Your mix inherits the Mastiff's calm indoor demeanor and the St. Bernard's sociable, outgoing nature. The result is a dog that's deeply bonded to family, tolerant of children, welcoming to guests, and content to spend most of the day lounging nearby. These dogs tend to be quiet indoors, rarely barking without cause, and they often show surprising spatial awareness for their size.
Challenging Temperament Scenarios
The Mastiff's guarding instinct can manifest as wariness toward strangers, territorial behavior around the property, or same-sex aggression. The St. Bernard's size combined with adolescent exuberance (roughly 8–18 months) can make leash walking genuinely dangerous — a 120-pound puppy pulling on a leash can injure an adult handler. Some individuals inherit the St. Bernard's stubborn streak, which makes training slower and requires more patience.
Training Approach
Force-free, positive reinforcement methods work best with this cross. Both breeds are sensitive despite their size — harsh corrections or aversive tools like prong collars and shock collars damage trust and can trigger fear-based reactivity in a dog that's too large to physically manage if they panic. Use high-value treats, marker-based training (clicker or verbal marker), and short 10–15 minute sessions. Giant breeds fatigue quickly during training, especially in warm weather.
Coat, Grooming, and the Shedding Reality
Is the English Mastiff and St. Bernard mix hypoallergenic? Absolutely not. This is a heavy-shedding cross, and no generation or breeding combination will change that. Neither parent breed carries the low-shedding coat genes found in breeds like Poodles.
Coat Type Possibilities
- Short coat (Mastiff-dominant): Dense, smooth, close-lying hair. Easier to brush but still sheds heavily seasonally.
- Medium coat (St. Bernard-dominant, short-hair parent): Slightly longer with a thicker undercoat. More prone to matting behind ears and on hindquarters.
- Long coat (St. Bernard long-hair parent): Significant feathering on legs, chest, and tail. Requires brushing 3–4 times per week to prevent tangles.
The specific coat your dog inherits depends entirely on which St. Bernard variety (short-hair or long-hair) was used in the cross. Ask the breeder which variety was the parent.
Grooming Routine
| Task | Frequency | Notes |
|---|---|---|
| Brushing | 2–4x per week | Use an undercoat rake (e.g., Furminator Giant Breed) during spring/fall shedding peaks |
| Bathing | Every 6–8 weeks | Use a large-breed wash station or professional groomer — home tubs rarely fit dogs over 150 lb |
| Nail trimming | Every 3–4 weeks | Overgrown nails alter gait and stress joints in giant breeds |
| Ear cleaning | Weekly | Floppy ears trap moisture — use a vet-recommended ear cleanser |
| Wrinkle/fold care | Daily to every other day | Mastiff-inherited facial folds need wiping with damp cloth to prevent yeast/bacterial infection |
| Drool management | Ongoing | Keep drool towels accessible; both breeds are prolific droolers |
Health Considerations: Hybrid Vigor vs. Giant Breed Reality
Let's address a common misconception directly: hybrid vigor does not eliminate health problems in this cross. The concept of heterosis (hybrid vigor) refers to the statistical tendency for crossbred animals to have slightly improved fitness traits compared to inbred purebreds. But when both parent breeds share the same structural health risks — which is exactly the case here — those risks carry through regardless of crossbreeding.
Both the English Mastiff and the St. Bernard are predisposed to a cluster of serious, expensive health conditions. Your mix inherits risk from both sides.
Inherited Health Conditions
| Condition | Prevalence in Parent Breeds | What to Watch For | Typical Treatment Cost |
|---|---|---|---|
| Hip Dysplasia | High — both breeds (OFA data shows 40–50% affected in some lines) | Hind leg lameness, bunny-hopping gait, reluctance to rise | $3,500–$7,000 per hip (surgical) |
| Elbow Dysplasia | Moderate to high in both breeds | Front leg lameness, stiffness after rest | $2,000–$5,000 per elbow |
| Gastric Dilatation-Volvulus (Bloat/GDV) | High risk — deep-chested giant breeds | Distended abdomen, unproductive retching, restlessness, collapse | $5,000–$10,000+ (emergency surgery) |
| Dilated Cardiomyopathy (DCM) | Present in both breeds, particularly Mastiffs | Coughing, exercise intolerance, fainting, abdominal swelling | $300–$800/month ongoing medication |
| Osteosarcoma (Bone Cancer) | Elevated in both giant breeds | Persistent lameness, swelling on a limb, pain on touch | $5,000–$15,000 (amputation + chemotherapy) |
| Entropion/Ectropion (Eyelid Issues) | Moderate — both breeds carry facial structure risks | Squinting, eye discharge, corneal irritation | $1,000–$3,000 (surgical correction) |
Preventive Health Plan
Work with your veterinarian to establish a screening protocol:
- OFA hip and elbow evaluations — baseline at 24 months
- Annual cardiac exam with echocardiogram starting at age 3
- Annual bloodwork to monitor organ function, especially if on joint supplements or NSAIDs
- Orthopedic Foundation for Animals (OFA) or PennHIP certifications should be requested from the breeder for both parent dogs
Always consult your veterinarian for personalized preventive care recommendations based on your individual dog's health profile.
Understanding Generations: F1, F2, and Beyond
- F1 (First Generation): One purebred English Mastiff parent × one purebred St. Bernard parent. Maximum genetic diversity, most predictable in terms of being a 50/50 mix — but individual puppies still vary in which parent they favor.
- F1B (First Generation Backcross): An F1 mix bred back to one of the parent breeds (e.g., F1 Saint Mastiff × English Mastiff). Results in 75/25 genetic split, leaning more heavily toward the backcross parent's traits.
- F2 (Second Generation): Two F1 mixes bred together. This is where trait variability increases dramatically — puppies may express traits from either grandparent line in unpredictable combinations.
- Multigen (F3+): Multiple generations of crossbreeding. Rare in this specific mix; most English Mastiff and St. Bernard crosses are F1 because the limited breeding pool makes sustained programs uncommon.
Most English Mastiff and St. Bernard mixes you'll encounter are F1 crosses. This is partly because the market for this specific combination is small — most giant breed enthusiasts prefer purebreds — and partly because breeding two 150+ lb dogs together carries logistical and welfare challenges that limit how many breeders attempt multigen programs.
With F1 crosses, you get the widest possible gene pool from two breeds, which may modestly reduce risk for conditions where the breeds differ genetically. But for shared risks (hip dysplasia, bloat, cardiac disease), the F1 generation carries the same baseline risk as either parent.
Cost: Purchase Price and Lifetime Ownership
Puppy Purchase Price
| Source | Price Range | What's Typically Included |
|---|---|---|
| Responsible Breeder (health-tested parents) | $1,500–$3,500 | OFA certifications, first vaccinations, deworming, health guarantee, take-back clause |
| Casual/Backyard Breeder | $800–$1,500 | Often no health testing, minimal veterinary care, no guarantee |
| Rescue/Adoption | $200–$600 | Spay/neuter, vaccinations, microchip — availability is rare for this specific mix |
A note on availability: this is not a common designer cross. You won't find English Mastiff and St. Bernard mix puppies listed regularly on breeder websites the way you find Goldendoodles or Labradoodles. Most available litters are one-off breedings. Giant breed rescues (such as Mastiff-specific or St. Bernard-specific rescues) occasionally take in mixes — check organizations like Mastiff Rescue or regional St. Bernard rescue networks.
Annual Ownership Costs
Owning a dog in the 150–250 lb range is significantly more expensive than owning a mid-size breed. Here's a realistic annual budget breakdown:
- Food: $1,800–$3,600/year (a 160 lb dog eats roughly 8–12 cups of high-quality kibble daily; giant breed formulas from brands like Royal Canin Giant, Purina Pro Plan Large Breed, or Hill's Science Diet Large Breed cost $60–$100 per 40-lb bag)
- Preventive medications: $600–$1,200/year (heartworm prevention, flea/tick — dosing for dogs over 100 lb costs significantly more; e.g., Heartgard Plus for 101+ lb dogs runs ~$130 for a 6-month supply)
- Routine veterinary care: $800–$1,500/year (exams, bloodwork, vaccines — giant breeds need more anesthesia for procedures, which increases costs)
- Pet insurance: $1,200–$2,400/year (giant breed premiums are steep; pre-existing condition exclusions make early enrollment critical)
- Supplies and gear: $400–$800/year (XXL beds, heavy-duty crates like the ProSelect Empire Dog Crate rated for 200+ lb dogs, reinforced leashes and harnesses)
- Emergency fund: Budget for at least $5,000–$10,000 in accessible savings for potential bloat surgery, orthopedic procedures, or cardiac treatment
Realistic first-year total: $8,000–$15,000 including puppy purchase. Ongoing annual cost: $5,000–$9,500.
Who Should (and Shouldn't) Consider This Mix
The English Mastiff and St. Bernard mix is not a beginner dog, and it's not an apartment dog. Here's an honest assessment of who this cross suits best.
Best Fit
- Experienced large-breed owners who have previously handled dogs over 100 lb and understand giant breed growth, nutrition, and training needs
- Homes with ground-floor access — stairs are destructive to developing giant breed joints, and carrying an injured 180 lb dog up steps is not feasible
- Families with older children (8+) — these dogs are gentle, but a 150 lb dog accidentally knocking over a toddler is a real injury risk
- Cooler climates — both breeds overheat easily, and a dog this size with a thick coat is at serious risk in hot, humid environments
- Owners with financial flexibility — veterinary care for giant breeds is 2–4x more expensive than for a 50 lb dog
- Patient trainers willing to invest 12–18 months in consistent socialization and obedience work using positive reinforcement methods
Poor Fit
- First-time dog owners
- Apartment or condo living (space and noise considerations — even though they're quiet, their size makes shared-wall living impractical)
- Homes with very young children or frail elderly members
- Hot climate regions without reliable air conditioning
- Tight budgets — a single emergency vet visit for bloat can exceed $8,000
- Anyone seeking a low-shedding or hypoallergenic dog
Frequently Asked Questions
What two breeds make up the English Mastiff and St. Bernard mix?
This cross combines a purebred English Mastiff with a purebred St. Bernard. Both are AKC-recognized Working Group breeds. The resulting puppies are first-generation (F1) designer crosses, inheriting traits from both parent breeds in varying proportions.
How big will an English Mastiff and St. Bernard mix get?
Expect males to reach 150–250+ lb (68–113+ kg) and females 120–190 lb (54–86 kg), with heights of 26–32+ inches at the shoulder. Full skeletal maturity takes 2–3 years. There is no reliable way to predict exact adult size from a puppy — paw size gives a rough indicator, but genetics and nutrition play the largest roles.
What is the temperament of this mix?
Most individuals are calm, affectionate, and loyal to family. Expect a dog that is gentle indoors but requires consistent training due to its size. Some inherit stronger guarding instincts from the Mastiff side, while others are more outgoing and playful like the St. Bernard. Early socialization between 8–16 weeks is critical for shaping a confident, well-adjusted adult.
Is the English Mastiff and St. Bernard mix hypoallergenic?
No. Neither parent breed carries low-shedding coat genetics. This mix sheds moderately to heavily year-round, with significant seasonal shedding peaks in spring and fall. It is not suitable for allergy-sensitive households.
What health issues might this mix inherit?
Shared risks between both parent breeds include hip dysplasia, elbow dysplasia, gastric dilatation-volvulus (bloat), dilated cardiomyopathy, osteosarcoma, and eyelid disorders (entropion/ectropion). Responsible breeders screen parent dogs through OFA or PennHIP certifications. Discuss a preventive screening plan with your veterinarian.
How much does an English Mastiff and St. Bernard mix cost?
Puppy prices range from $1,500–$3,500 from responsible breeders who health-test parent dogs. Adoption fees from rescue organizations are typically $200–$600, though this specific mix is rarely available through rescue. Annual ownership costs run $5,000–$9,500, with first-year expenses often exceeding $10,000.
How long do English Mastiff and St. Bernard mixes live?
Expect a lifespan of 7–10 years. Giant breeds age faster than smaller dogs, and both parent breeds have relatively short lifespans. Maintaining a lean body condition score (BCS 4–5 on a 9-point scale), feeding a giant-breed-appropriate diet, and keeping up with preventive veterinary care can help maximize both longevity and quality of life.
Tom Renshaw
All our authors care for dogs every day — read more of their work on the authors page.
