St Bernard and English Mastiff Mix

When you cross two of the largest dog breeds on the planet, you get what some breeders call the "Saint Mastiff" — a St Bernard and English Mastiff mix that can tip the scales at over 200 pounds. This is not a dog for first-time owners or small apartments. But for the right household, this gentle giant cross offers loyalty, calm companionship, and a truly awe-inspiring presence.

This guide breaks down everything you need to know about the St Bernard and English Mastiff mix before you commit — including the traits you can predict, the ones you can't, and the real costs (financial and lifestyle) of living with a dog this size.

Parent Breed Breakdown: St Bernard Meets English Mastiff

Understanding any mixed breed starts with understanding its parent breeds. The St Bernard and English Mastiff share some traits — massive size, gentle temperament, deep loyalty — but differ in important ways that influence what their offspring might look and act like.

Parent Breed Comparison: St Bernard vs. English Mastiff

Trait	St Bernard (AKC Standard)	English Mastiff (AKC Standard)
Weight Range	120–180 lb (54–82 kg)	120–230 lb (54–104 kg)
Height at Shoulder	26–30 in (66–76 cm)	27.5–32+ in (70–81+ cm)
Lifespan	8–10 years	6–10 years
Coat Type	Short smooth or long rough; dense undercoat	Short, straight, moderate density
Shedding Level	Moderate to heavy (seasonal blow-out)	Moderate year-round
Energy Level	Low to moderate	Low
Original Purpose	Alpine rescue, draft work	Guardian, estate protector
Temperament Hallmarks	Outgoing, playful, eager to please	Dignified, reserved with strangers, courageous
Drool Factor	High (loose lips, deep flews)	High (heavy flews, wide muzzle)

Both breeds are classified as Working Group dogs by the American Kennel Club, meaning they were developed for physical tasks rather than companionship alone. That working heritage shows up in their offspring as a desire to have a job — even if that "job" is supervising the backyard from a shaded spot on the porch.

Generation Types: What F1, F1B, and Multigen Mean for This Mix

In practice, the vast majority of St Bernard and English Mastiff mixes you'll encounter are F1 crosses. This is a relatively niche designer pairing — unlike Labradoodles or Goldendoodles, there's no large-scale multigen breeding program for Saint Mastiffs. That means you're almost always looking at a first-generation cross with maximum trait variability.

Size Range: How Big Does a St Bernard and English Mastiff Mix Get?

This is where genetics gets interesting — and where prospective owners need to plan carefully. Both parent breeds are giants, but the English Mastiff holds the record for one of the heaviest dog breeds in the world.

Saint Mastiff Size Range Estimates

Measurement	Lower End (St Bernard–Leaning)	Upper End (Mastiff–Leaning)
Adult Weight (Male)	140–170 lb (64–77 kg)	180–230+ lb (82–104+ kg)
Adult Weight (Female)	120–150 lb (54–68 kg)	150–190 lb (68–86 kg)
Height at Shoulder (Male)	27–29 in (69–74 cm)	30–33 in (76–84 cm)
Height at Shoulder (Female)	25–28 in (64–71 cm)	28–31 in (71–79 cm)
Full Maturity Age	18–24 months	24–36 months

Giant breeds grow slowly. Don't expect a Saint Mastiff to reach full skeletal maturity until 24–36 months. During the growth phase, it's critical to feed a large-breed puppy formula (look for the AAFCO statement specifying growth for large breeds, meaning the formula meets calcium and phosphorus ratios for dogs expected to reach 70+ lb at maturity). Overfeeding a growing giant-breed puppy increases the risk of developmental orthopedic diseases like hip dysplasia and osteochondrosis.

Practical tip: A fully grown male Saint Mastiff leaning toward the Mastiff side may need an XXL crate (54-inch minimum). Budget $150–$300 for a heavy-duty crate rated for 200+ lb dogs. Standard vehicle cargo areas may not accommodate a dog this size — measure your SUV or truck bed before committing.

Coat Type, Shedding, and Grooming: What to Expect

Coat inheritance in the Saint Mastiff depends heavily on which St Bernard variant is in the pedigree. The St Bernard comes in two coat types — smooth (short) and rough (long) — while the English Mastiff carries genes for a short, dense coat.

Coat Scenarios

• Short-coat St Bernard × Mastiff: Puppies will almost certainly have short, dense coats similar to the Mastiff parent. Moderate year-round shedding with seasonal increases. This is the most common outcome.
• Long-coat (rough) St Bernard × Mastiff: Puppies may inherit a medium-length coat with moderate feathering on the legs, chest, and tail. Shedding is heavier, and matting can occur behind the ears and on the hindquarters if not brushed regularly.
• Mixed expression: In F1 litters, some puppies may inherit a medium-length coat while littermates get the short variety. You cannot predict this at birth — coat texture becomes apparent around 8–12 weeks.

Is this mix hypoallergenic or low-shedding? No. Neither parent breed carries the low-shedding gene variants found in Poodles or Bichon Frises. Expect moderate to heavy shedding regardless of coat type. If allergies are a concern in your household, this is not the right mix.

Grooming Routine

Task	Short Coat	Medium/Long Coat
Brushing	2–3× per week (rubber curry brush or bristle brush)	3–4× per week (slicker brush + undercoat rake during shedding season)
Bathing	Every 6–8 weeks or as needed	Every 4–6 weeks; may need blow-dry to prevent skin moisture trapping
Ear Cleaning	Weekly (both breeds have drop ears prone to infection)	Weekly
Nail Trimming	Every 2–3 weeks (giant breeds put significant weight on nails)	Every 2–3 weeks
Drool Management	Daily face wiping; drool bibs recommended	Daily face wiping; coat around muzzle may need trimming

Invest in a high-velocity dryer ($80–$150, brands like Flying Pig or Shelandy) for bath days. Air-drying a 180-pound dog with a medium coat takes hours and can lead to hot spots if moisture gets trapped against the skin.

Temperament: The Best-Case and Challenging Scenarios

Temperament is where the St Bernard and English Mastiff mix can be genuinely wonderful — or genuinely challenging — depending on which parent's traits dominate and, crucially, how the dog is socialized during the critical 3–16 week window.

Best-Case Temperament Profile

The ideal Saint Mastiff inherits the St Bernard's outgoing friendliness and the Mastiff's steady confidence. This produces a dog that is:

• Calm and low-energy indoors (couch-potato lifestyle compatible)
• Affectionate and physically demonstrative (leans, laps, full-body wags)
• Tolerant of children and other pets when properly socialized
• Alert and observant without excessive barking
• Responsive to training with food motivation (both breeds are food-driven)

Challenging Temperament Scenarios

Less ideal outcomes can include:

• Mastiff-dominant wariness: Some individuals inherit the Mastiff's natural suspicion of strangers, which without extensive early socialization can develop into territorial behavior that's difficult to manage in a 200-pound dog.
• Stubbornness plateau: Both breeds are known for an independent streak. The Mastiff in particular was bred to make its own decisions as a guardian. Combine that with the St Bernard's "I'll get to it eventually" attitude and training sessions require patience and creativity.
• Adolescent testing: Giant breeds have extended adolescence (up to 3 years). Expect a prolonged period where your dog "forgets" previously learned commands. Consistency during this phase is non-negotiable.

Training approach: Use positive reinforcement exclusively — food rewards, praise, play. Both breeds respond poorly to harsh corrections, which can trigger shutdown (St Bernard tendency) or defensive resistance (Mastiff tendency). Force-free methods from a certified trainer (look for CPDT-KA or IAABC credentials) are strongly recommended, especially during the adolescent phase. A 6-foot leash and front-clip harness (such as the Ruffwear Front Range or Kurgo Tru-Fit in XL/XXL) give you better control during walks without risking tracheal damage.

Health Considerations: Hybrid Vigor, Myths, and Real Risks

Let's address the elephant — or in this case, the mastiff — in the room: hybrid vigor does not eliminate health risks in this mix. The concept of heterosis (hybrid vigor) applies most strongly to traits controlled by many genes with simple recessive inheritance patterns. Many of the serious conditions affecting both parent breeds involve complex polygenic inheritance or structural conformation issues that a crossbreeding does not automatically fix.

Because both the St Bernard and the English Mastiff share several health vulnerabilities, a Saint Mastiff cross has a meaningful probability of inheriting these conditions:

Shared and Parent-Specific Health Risks

Condition	Shared Risk?	Prevalence Notes	Screening Recommendation
Hip Dysplasia	Yes — both breeds	St Bernard: ~47% affected (OFA data); Mastiff: ~20% affected	PennHIP or OFA evaluation on parents
Elbow Dysplasia	Yes — both breeds	Higher in St Bernards; OFA recommends screening	OFA elbow evaluation on parents
Dilated Cardiomyopathy (DCM)	Yes — both breeds	St Bernards have elevated DCM rates; Mastiffs prone to cardiomyopathy	Cardiac evaluation (OFA) + echocardiogram on parents
Gastric Dilatation-Volvulus (Bloat/GDV)	Yes — deep-chested giants	Both breeds are among the highest-risk for GDV; lifetime risk estimated 5–10%+	Discuss prophylactic gastropexy with your vet
Osteosarcoma	Yes — large/giant breeds	St Bernards have one of the highest breed-specific rates	No screening test; monitor for lameness/swelling
Entropion/Ectropion	Yes — loose facial skin	Common in both breeds due to heavy facial folds	Ophthalmologist evaluation (OFA/CERF)
Hypothyroidism	Primarily St Bernard	Autoimmune thyroiditis documented in St Bernard lines	Thyroid panel on St Bernard parent
Cystinuria	Primarily English Mastiff	Mastiffs are among breeds with documented cystine bladder stones	Urine amino acid screening on Mastiff parent

Bloat prevention is critical. According to the Merck Veterinary Manual, GDV is a life-threatening emergency with a mortality rate of 10–30% even with surgical treatment. For a dog this size, emergency GDV surgery can cost $5,000–$10,000+. Discuss prophylactic gastropexy (stomach tacking) with your veterinarian at the time of spay/neuter — this preventive procedure reduces GDV risk by over 90%.

Feeding protocol to reduce bloat risk:

• Feed 2–3 smaller meals per day (never one large meal)
• Use a slow-feeder bowl (Outward Hound Fun Feeder in XL works for giant breeds)
• No vigorous exercise 60 minutes before or after meals
• Avoid elevated food bowls — research from a Purdue University study published in JAVMA found elevated feeders actually increased GDV risk in large and giant breeds

Cost of Ownership: Purchase Price and Annual Expenses

Owning a St Bernard and English Mastiff mix is a significant financial commitment. Here's a realistic breakdown based on 2026 market data:

Acquisition Costs

Source	Price Range	Notes
Responsible Breeder (health-tested parents)	$1,500–$3,500	Rare cross; limited breeder availability. Expect waitlists of 6–12 months. Insist on OFA/PennHIP certificates for both parents.
Backyard Breeder / Online Listings	$500–$1,500	No health testing, no genetic screening, no take-back clause. High risk of inherited conditions. Not recommended.
Breed-Specific Rescue	$300–$600	Check St Bernard rescue networks (e.g., Saint Bernard Rescue Foundation) and Mastiff rescue groups (e.g., Mastiff Rescue). Mixed breeds sometimes appear, but availability is unpredictable.
General Shelter / Humane Society	$50–$350	Occasionally giant-breed mixes are surrendered. DNA testing (Embark or Wisdom Panel, ~$100–$200) can confirm parentage.

First-Year Estimated Costs

Expense Category	Estimated Cost
Food (large-breed formula, 50–80 lb bags)	$1,200–$2,400/year
Veterinary (wellness, vaccines, heartworm, flea/tick)	$800–$1,500
Spay/Neuter (giant-breed pricing)	$400–$900
Prophylactic Gastropexy (if combined with spay/neuter)	$300–$800 additional
Crate (54-inch heavy-duty)	$150–$350
Bed (orthopedic, XL/XXL)	$100–$300
Harness, leash, collar (XXL sizing)	$80–$200
Training (puppy class + adolescent refresher)	$200–$600
Pet Insurance (giant-breed monthly premium)	$80–$150/month ($960–$1,800/year)
Total First-Year Estimate	$4,200–$8,850+

Insurance note: Pet insurance premiums for giant breeds are substantially higher than average because veterinary costs scale with body weight (more medication per dose, larger surgical supplies, specialized imaging tables). Enroll before your puppy is 6 months old to avoid pre-existing condition exclusions. Companies like Trupanion, Healthy Paws, and Fetch offer giant-breed plans, but read the fine print on hereditary condition coverage and annual payout caps.

Who Is This Mix Best Suited For?

The St Bernard and English Mastiff mix is not a versatile "fits every home" dog. Here's an honest assessment of who thrives with this cross — and who should consider a different breed.

For the right owner, the Saint Mastiff cross is an extraordinary companion — deeply bonded, surprisingly gentle, and endlessly entertaining in their clumsy, oversized way. But going in with eyes open about the size, health risks, costs, and lifestyle adjustments is the difference between a successful lifelong partnership and a heartbreaking surrender to rescue.

Frequently Asked Questions

What two breeds make up the Saint Mastiff mix?

The Saint Mastiff is a cross between a St Bernard and an English Mastiff. Both are AKC Working Group breeds originally developed for physically demanding tasks — alpine rescue and drafting (St Bernard) and estate guarding (English Mastiff). The mix is sometimes called the Saint Mastiff, Mastiff Bernard, or simply a St Bernard-Mastiff cross.

How big will a St Bernard and English Mastiff mix get?

Adult males typically weigh 140–230+ lb (64–104+ kg) and stand 27–33 inches (69–84 cm) at the shoulder. Females are somewhat smaller at 120–190 lb (54–86 kg) and 25–31 inches (64–79 cm). Exact size depends on which parent's genes dominate. Full maturity takes 24–36 months.

What will the temperament be like?

Expect a calm, affectionate, low-to-moderate energy dog that bonds closely with family. The St Bernard side contributes playfulness and sociability; the Mastiff side contributes dignity and protectiveness. Early socialization (starting by 8 weeks) and consistent positive-reinforcement training are essential. Individual temperament varies significantly between littermates.

Is the St Bernard and English Mastiff mix hypoallergenic?

No. Neither parent breed carries low-shedding coat genes. This mix sheds moderately to heavily year-round, with increased shedding during seasonal coat changes. It is not suitable for households with dog allergies.

What health issues might this mix inherit?

Key concerns shared by both parent breeds include hip dysplasia, elbow dysplasia, dilated cardiomyopathy, gastric dilatation-volvulus (bloat), osteosarcoma, and eye conditions (entropion/ectropion). Responsible breeders should provide OFA or PennHIP certifications for hips and elbows, cardiac evaluations, and ophthalmologist clearances for both parents. Consult your veterinarian about a breed-appropriate health screening schedule.

How much does a St Bernard and English Mastiff mix cost?

From a responsible breeder with health-tested parents, expect to pay $1,500–$3,500. Rescue adoption fees range from $50–$600. First-year total costs (food, veterinary, supplies, insurance) typically run $4,200–$8,850+. This is one of the most expensive mixed breeds to maintain due to giant-breed food quantities, medication dosages, and insurance premiums.