Big dogs don’t just grow—they unfold.
From clumsy, oversized puppies to towering, couch-hogging adults, these breeds take their sweet time becoming the giants they’re destined to be.
They gallop through life with paws too big for their bodies, ears that flap like sails, and hearts that seem to grow just as fast as their frames. Watching them mature is like witnessing slow-motion magic. One day, they’re tripping over their own feet—next thing you know, they’re eye-level at the dinner table.
These gentle giants don’t just take up space—they own it. And for those who love a dog with presence, personality, and plenty of drool, they’re impossible to resist.
Let’s meet the 18 massive dog breeds that take the longest to grow up—but are absolutely worth the wait.
Saint Bernard
With a heritage rooted in the Swiss Alps, Saint Bernards are known for their rescue missions in treacherous terrain. These gentle giants can weigh up to 180 pounds and take around two to three years to reach their full size.
Their calm and patient demeanor makes them ideal family pets. Despite their size, they are known for being gentle with children, often displaying a nurturing instinct.
Did you know? Saint Bernards were originally bred to rescue travelers lost in the snowy Alps, using their keen sense of direction and strength to save lives.
Great Dane
Regal and statuesque, Great Danes are often referred to as the “Apollo of dogs.” These striking creatures are one of the tallest breeds, with some reaching over 30 inches at the shoulder.
Great Danes take approximately two to three years to reach their full height and weight. Despite their imposing size, they are known for their friendly and affectionate nature.
Fun fact: The Great Dane is the national dog of Germany, where it was originally bred to hunt wild boar. Their courage and strength are legendary.
Newfoundland
With a heart as big as its paws, the Newfoundland is every child’s gentle guardian. These water-loving dogs are known for their impressive swimming skills and life-saving instincts.
Newfoundlands can weigh up to 150 pounds and take about two years to fully mature. Their sweet temperament and gentle nature make them wonderful companions for families.
Did you know? Newfoundlands have webbed feet, which aid them in swimming. They have been known to rescue people from drowning, earning them the nickname “nanny dogs.”
Leonberger
Named after the German city of Leonberg, Leonbergers are known for their lion-like appearance and noble stature. These dogs are gentle giants, weighing up to 170 pounds.
It takes them approximately 2.5 years to reach their full size. Their friendly and outgoing nature makes them excellent companions for children and adults alike.
Interesting tidbit: Leonbergers were originally bred as companion animals for European royalty. Their regal presence and gentle demeanor made them favorites among the aristocracy.
Mastiff
The Mastiff, with its imposing size and gentle eyes, is a breed that commands attention. Known for their loyalty and protective nature, Mastiffs can weigh upwards of 200 pounds.
These dogs take around three years to reach their full stature. Despite their large size, they are incredibly gentle and affectionate with their families.
Historical note: Mastiffs have been depicted in art and literature for centuries, and were once used as war dogs in ancient armies. Today, they are beloved for their calm and stable demeanor.
Tibetan Mastiff
The Tibetan Mastiff is a breed shrouded in mystery and legend. Known for their independence and strong-willed nature, these dogs take about four years to fully mature.
Weighing in at up to 160 pounds, they are protective and loyal to their families. Their thick coats make them well-suited for cold climates.
Did you know? Tibetan Mastiffs were traditionally used by nomadic cultures in the Himalayas to guard sheep from predators like wolves and leopards. Their fearlessness and loyalty are unmatched.
Irish Wolfhound
The Irish Wolfhound’s grace and size are unmatched in the canine world. As one of the tallest breeds, they can stand over 32 inches tall at the shoulder.
It takes approximately two years for these gentle giants to reach their full size. They are known for their calm and friendly disposition, making them excellent companions.
Fun fact: The Irish Wolfhound was originally bred to hunt wolves in Ireland, and their courage in the field is legendary. Despite their hunting prowess, they are gentle and loving at home.
Bernese Mountain Dog
Known for their striking tri-color coats, Bernese Mountain Dogs are beloved for their joyful personalities. These dogs can weigh up to 115 pounds and take about 2.5 years to reach full maturity.
Their playful and affectionate nature makes them great family pets, especially in homes with children. They thrive in cold climates, thanks to their thick coats.
A bit of history: Originally from the Swiss Alps, Bernese Mountain Dogs were used as draft animals and farm helpers. Their strength and agility make them versatile working dogs.
Dogue de Bordeaux
With its distinctive wrinkled face and muscular build, the Dogue de Bordeaux is a breed with a rich history. These dogs can weigh up to 140 pounds and take about two years to reach full size.
Known for their loyalty and protective instincts, they are devoted family pets. Despite their imposing appearance, they are gentle and affectionate with those they love.
Historical tidbit: The Dogue de Bordeaux is one of the oldest French breeds, originally used for guarding estates and hunting large game. Their courage and strength are well-documented.
Alaskan Malamute
The Alaskan Malamute, with its wolf-like appearance, takes around 2 to 3 years to fully grow into its robust body. Known for their endurance and strength, they were historically used for hauling heavy freight.
Their long maturation period complements their energetic and friendly disposition. These dogs thrive in cold climates, where their thick coats protect them from harsh weather.
An embodiment of resilience, the Malamute’s growth journey is as adventurously spirited as their role in the icy wilderness.
Pyrenean Mastiff
The Pyrenean Mastiff is a breed known for its tranquility and strength. These dogs can weigh over 180 pounds and take approximately 2.5 years to reach their full size.
Their calm and gentle nature makes them wonderful family companions. Pyrenean Mastiffs are known for their protective instincts, especially with children.
Interesting fact: Originally from the Pyrenees Mountains of Spain, these dogs were used to guard livestock. Their ability to protect flocks from predators is legendary, combining vigilance with gentleness at home.
Anatolian Shepherd
The Anatolian Shepherd is known for its independence and protective nature. Weighing up to 150 pounds, these dogs take about two years to fully mature.
They are incredibly loyal and make excellent guardians for livestock and families alike. Their calm demeanor belies their keen instincts and strength.
Did you know? Anatolian Shepherds have been used for centuries in Turkey to guard flocks against predators. Their courage and loyalty are celebrated in their homeland, making them both revered and respected.
Greater Swiss Mountain Dog
Often referred to as the “Swissy,” this breed’s growth story is as striking as its appearance. Known for its sturdy build and tri-color coat, the Greater Swiss Mountain Dog takes about 2 to 3 years to fully mature.
Their slow maturation ensures a balanced temperament, making them reliable companions. Historically, they were revered for their strength and endurance, often utilized as working dogs in the Swiss Alps.
The breed’s patience in reaching full size is mirrored in their calm and composed demeanor, a trait cherished by owners.
Komondor
The Komondor, with its unique corded coat, is a breed that stands out in any crowd. These dogs weigh up to 130 pounds and take about three years to reach their full size.
Known for their guarding instincts, Komondors are protective and loyal to their families. Their distinctive appearance is both practical and striking.
Interesting tidbit: Originally from Hungary, Komondors were used to guard livestock. Their corded coats provide protection from harsh weather and predators, making them excellent guardians in rural areas.
Caucasian Shepherd Dog
Known for its strength and resilience, the Caucasian Shepherd Dog is a formidable guardian. Weighing between 110 to 220 pounds, these dogs take approximately three years to fully mature.
Their protective instincts are unrivaled, making them ideal for guarding livestock and property. Despite their size, they are gentle with family members.
Did you know? Caucasian Shepherd Dogs originate from the Caucasus Mountains, where they have been used for centuries to protect flocks from predators like bears and wolves. Their bravery and loyalty are legendary.
Boerboel
The Boerboel, with its strength and protective nature, is a breed of South African origin. Weighing up to 200 pounds, these dogs take about two years to reach their full size.
Boerboels are known for their loyalty and courage, making them excellent protectors of their families. Despite their strong-willed nature, they are affectionate and gentle with those they love.
Fun fact: Boerboels were originally bred by Dutch settlers in South Africa to protect homesteads from predators. Their formidable presence and bravery are renowned.
Akbash
Serenity and protectiveness define the Akbash. These dogs, weighing between 75 to 140 pounds, take about two years to mature fully.
Their calm and gentle demeanor makes them excellent family companions, while their protective instincts are highly valued in guarding livestock.
Did you know? The Akbash originates from Turkey and has been used for centuries as a guardian of flocks. Their white coats blend with sheep, offering them the advantage of surprise against predators. Their loyalty and vigilance are esteemed traits.
Borzoi
Often referred to as the ‘Russian Wolfhound,’ the Borzoi captivates with its graceful demeanor and regal appearance. Originating from Russia, this breed was prized by nobility for its speed and hunting prowess. Borzois are known for their long, flowing coats and slender, athletic builds.
These dogs can take up to three years to reach their full size, gradually developing both physically and mentally. Their personalities are as captivating as their looks, often described as reserved yet affectionate.
A lesser-known fact is that Borzois were once used by Russian aristocrats for hunting wolves, showcasing their strength and agility.