Giant dog breeds can take years to reach their full size and maturity, unlike their smaller cousins.
These gentle giants often maintain puppy-like behaviors well into adulthood, making them both entertaining and occasionally challenging for their owners. Here’s a look at massive canines that take the slow route to growing up!
1. Great Dane: The Apollo Of Dogs
Standing nearly three feet tall at the shoulder, Great Danes don’t reach full physical maturity until age 2-3. Their gangly teenage phase is particularly amusing.
Despite their imposing size, these dogs remain puppy-like in their clumsiness and desire for lap cuddles even when they’re 130+ pounds. Many owners report their Danes still think they’re small puppies well into their adult years.
2. Saint Bernard: Mountain-Sized Babies
Famous for rescue missions in the Alps, Saint Bernards grow at a glacial pace, taking 2-3 years to reach their full 180-pound potential. During this extended adolescence, they’re known for their comical clumsiness.
A fully grown Saint Bernard often forgets its size, attempting to squeeze into tiny spaces or hide under furniture. Their slow maturation extends to their minds too – many remain playful and mischievous well into adulthood.
3. Newfoundland: Water-Loving Gentle Giants
Bred as working dogs for Canadian fishermen, Newfoundlands take nearly three years to reach their impressive 150-pound adult weight. Their growth journey includes an extended awkward phase with disproportionate paws and legs.
Surprisingly agile swimmers from a young age, these dogs develop their famous water rescue abilities long before they finish growing. Their sweet temperament remains constant from puppyhood through adulthood, making the growth process easier on owners.
4. Irish Wolfhound: Tallest Of All Canines
Reaching heights of nearly 3 feet at the shoulder, Irish Wolfhounds don’t stop growing until they’re about 3 years old. These historic sighthounds were once used to hunt wolves in Ireland.
Young wolfhounds experience dramatic growth spurts that often leave them uncoordinated and puzzled by their changing bodies. Their characteristic laid-back personality develops early, but their massive frame takes years to catch up with their gentle hearts.
5. Leonberger: Lion-Like Later Bloomers
Originally bred to resemble lions, these German giants take a full 3 years to develop their magnificent manes and reach their 150-pound adult weight. Leonberger puppies are born small but grow at an astonishing rate.
Young Leonbergers often display endearing contradictions – eager to work and please, yet goofy and unaware of their size. Their webbed feet make them natural swimmers from an early age, even while the rest of their body is still catching up.
6. English Mastiff: Ancient Giants With Baby Faces
Holding world records for heaviest dogs, English Mastiffs can reach over 200 pounds and take a full 3-4 years to completely mature. Their wrinkled faces remain puppy-like even as their bodies expand to massive proportions.
Young Mastiffs grow in spurts, often waking up noticeably bigger after a good night’s sleep. Their infamous drooling habit develops early, but their legendary guardian instincts take years to fully mature alongside their imposing frames.
7. Bernese Mountain Dog: Alpine Puppies For Years
Recognizable by their striking tri-color coats, Bernese Mountain Dogs grow steadily for about 2-3 years before reaching their full 115-pound potential. Their growth pattern often surprises owners who expect faster maturation.
Young Berners maintain their puppy enthusiasm for snow and cold weather from day one. Despite their size, many insist on being lap dogs throughout their extended adolescence, creating comical situations as they continue growing while still demanding cuddles.
8. Cane Corso: Italian Protectors With Extended Youth
With ancient Roman lineage, these powerful Italian Mastiffs take around 2 years to reach physical maturity but may not be mentally mature until age 3. Their muscular development happens in visible stages throughout puppyhood.
Young Corsos experience a fascinating transformation from wrinkly puppies to sleek, athletic adults. Their protective instincts emerge early, but the self-control to manage these instincts appropriately takes much longer to develop, requiring patient training throughout their extended adolescence.
9. Anatolian Shepherd: Livestock Guardians In Training
Hailing from Turkey, these independent guardians reach full size around 2 years but continue developing their protective instincts and judgment until age 3. Their growth is steady rather than occurring in dramatic spurts.
Young Anatolians display their guardian heritage early, practicing protective behaviors long before they’re fully grown. Their legendary independence can make training challenging during their extended adolescence, as they’re naturally programmed to make decisions without human input.
10. Tibetan Mastiff: Himalayan Guardians With Prolonged Puppyhood
Sporting magnificent lion-like manes, Tibetan Mastiffs take an extraordinary 3-5 years to fully mature both physically and mentally. Their massive double coats develop slowly, with puppies looking completely different from adults.
Young Tibetans experience dramatic seasonal changes, “blowing” their puppy coats in spectacular fashion. Their legendary aloofness toward strangers develops gradually – many are surprisingly social as puppies before growing into their more reserved adult personalities.
11. Dogue De Bordeaux: French Mastiffs With Baby Faces
Made famous in “Turner & Hooch,” these wrinkly French giants reach their full 140-pound potential around age 2-3. Their distinctive massive heads develop proportionally slower than the rest of their bodies.
Young Dogues maintain their adorable worried expressions into adulthood. Their growth journey includes an awkward phase where their bodies seem too big for their legs, creating a comical waddling gait that eventually transforms into the powerful stride of maturity.
12. Neapolitan Mastiff: Walking Wrinkles That Keep Expanding
Famous for excessive wrinkles and loose skin, Neapolitan Mastiffs grow slowly for 3+ years, reaching weights of 150+ pounds. Their skin actually “grows” before their bodies, creating their characteristic droopy appearance.
Watching a Neo puppy mature is like witnessing a walking wrinkle transform into a living sculpture. Their distinctive head shape develops gradually, with the jowls and dewlaps becoming more pronounced with age, while their puppy-like attachment to their humans remains unchanged.
13. Great Pyrenees: Majestic Mountain Guardians
Sporting gorgeous white coats, Great Pyrenees can take up to 3 years to reach full maturity. Their growth pattern includes developing the double dewclaws on their hind legs – a unique breed characteristic.
Young Pyrs display their guardian instincts from puppyhood, often “patrolling” their territories before they’re fully grown. Their famous independence and occasional stubbornness appear early, but their judgment about what actually constitutes a threat takes years to develop.
14. Caucasian Shepherd: Ancient Guardians With Prolonged Development
Originating in the Caucasus Mountains, these massive guardians take an impressive 3-4 years to reach their full potential of up to 200 pounds. Their thick double coats develop seasonally throughout their extended growth period.
Young Caucasians experience dramatic physical transformations from fluffy puppies to imposing adults. Their naturally protective temperament appears early, but the wisdom to correctly assess threats takes years to develop, making early socialization and training essential during their lengthy maturation.
15. Black Russian Terrier: Soviet-Created Giants
Despite “terrier” in their name, these massive working dogs reach 130 pounds and take 2-3 years to fully mature. Developed by the Soviet military, they grow at a measured pace that belies their eventual power.
Young BRTs experience a fascinating coat transformation, with their distinctive beards and leg furnishings developing gradually. Their intelligent, watchful nature appears early, but their confidence and working abilities continue developing long after they reach full size.