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Mastiff puppies and dogs in Boulder, Colorado

Looking for a Mastiff puppy or dog in Boulder, Colorado? Adopt a Pet can help you find an adorable Mastiff near you.

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Adopt a Mastiff near you in Boulder, Colorado

These Mastiffs are available in Boulder, Colorado.
Photo of Gumbo

Gumbo

Mastiff

Male, 1 yr 8 mos
Boulder, CO
Size
(when grown) Large 61-100 lbs (28-45 kg)
Details
-
Story
Handsome Gumbo! This sweet boy is searching for a new home, could he be the right one for you? Gumbo loves pets and people, but can get overwhelmed at times and will benefit from an adopter that can support him when he needs it! He has also enjoyed the company of other dogs and might do well in a multi-dog home. At this time, HSBV will only rehome him to a family either without children or with children over the age of 10.Gumbo can be met with until 4:30pm so our Training & Behavior team can provide adoption counseling.

Or, how about these Mastiffs in cities near Boulder, Colorado

These Mastiffs are available for adoption close to Boulder, Colorado.
Photo of Gumbo

Gumbo

Mastiff

Male, 1 yr 8 mos
Boulder, CO
Size
(when grown) Large 61-100 lbs (28-45 kg)
Details
-
Story
Handsome Gumbo! This sweet boy is searching for a new home, could he be the right one for you? Gumbo loves pets and people, but can get overwhelmed at times and will benefit from an adopter that can support him when he needs it! He has also enjoyed the company of other dogs and might do well in a multi-dog home. At this time, HSBV will only rehome him to a family either without children or with children over the age of 10.Gumbo can be met with until 4:30pm so our Training & Behavior team can provide adoption counseling.
Special Needs
No photo available for Sabrina

Sabrina

Mastiff American Bulldog

Female, 7 yrs 8 mos
Boulder, CO
Size
(when grown) X-Large 101 lbs (46 kg) or more
Details
Needs special attention, Needs experienced adopter, House-trained, Spayed or Neutered, Shots are up-to-date,
Story
Meet Sabrina, a gentle 6-year-old Mastiff mix who’s in need of a special forever home. Sabrina is living with mast cell tumors (MCT) due to cancer and is currently on medication to keep her as comfortable as possible. She requires a loving home that is prepared to offer her hospice care and a peaceful environment. Sabrina can be shy with new people and may give a warning growl or snap if approached when she’s not ready. However, once she builds trust, she becomes deeply affectionate and very attached to her people. She gets along well with mellow dogs and will thrive in a calm household where she can feel safe and loved. If you have a compassionate heart and are ready to provide a supportive and caring home for a special dog like Sabrina, you’ll find a loyal and loving companion in her.
Photo of Huckleberry

Huckleberry

Mastiff

Male, 1 yr 1 mo
Denver, CO
Size
(when grown) Large 61-100 lbs (28-45 kg)
Details
Good with dogs, House-trained, Spayed or Neutered, Shots are up-to-date,
Story
I’m Huckleberry, a 1 year  old male Mastiff mix. ********PLEASE READ BELOW PRIOR TO EMAILING IN**********If you are interested in adopting this dog or any other from our rescue, please go to https://www.hobocare.org/adopt to review our home requirements and fill out an application. Please do not email and ask for more information on how to adopt, all the information is already available online. The information you see here is all that is currently available about this dog. No boxers are adopted without a completed application and home check. Thank you! ##2619848##
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Photo of Cove

Cove

Mastiff Great Pyrenees

Female, 1 mo
Aurora, CO
Size
(when grown) Large 61-100 lbs (28-45 kg)
Details
Good with kids, Good with dogs, Good with cats, Spayed or Neutered, Shots are up-to-date,
Story
Meet this splashingly adorable puddle of puppies! Introducing Cove, Sea, Brook, Ocean, Reef, Harbor, Bayou, Lake & Creek! They are ready to send waves of love, fun, and playfulness right into your homes. Born to their mama Freya, these pups are going to make excellent dogs. They are a great mix of Great Pyrenees, Mastiff and who knows what- so they are sure to be big pups. NOTE: They will be available to meet at the PetSmart Adoption Event in Springfield, MO on Saturday, June 20. Come meet them and take one home! If you're interested in adopting me, please fill out an application at www.polkcountyhumanesociety.org/adopt. You can also reserve an appointment to meet me. Some pets are in foster homes or may already have visits scheduled, so appointments help ensure I’ll be available. Polk County Humane Society is located in Bolivar, Missouri, and we welcome adopters from any state. We have access to a transport to Aurora, CO. Other out of state adopters either travel to Missouri or arrange & pay for air transport. Virtual meet and greets are available on the appointment request. ##2755247##
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Photo of Ocean

Ocean

Mastiff Great Pyrenees

Female, 1 mo
Aurora, CO
Size
(when grown) Large 61-100 lbs (28-45 kg)
Details
Good with kids, Good with dogs, Good with cats, Spayed or Neutered, Shots are up-to-date,
Story
Meet this splashingly adorable puddle of puppies! Introducing Cove, Sea, Brook, Ocean, Reef, Harbor, Bayou, Lake & Creek! They are ready to send waves of love, fun, and playfulness right into your homes. Born to their mama Freya, these pups are going to make excellent dogs. They are a great mix of Great Pyrenees, Mastiff and who knows what- so they are sure to be big pups. NOTE: They will be available to meet at the PetSmart Adoption Event in Springfield, MO on Saturday, June 20. Come meet them and take one home! If you're interested in adopting me, please fill out an application at www.polkcountyhumanesociety.org/adopt. You can also reserve an appointment to meet me. Some pets are in foster homes or may already have visits scheduled, so appointments help ensure I’ll be available. Polk County Humane Society is located in Bolivar, Missouri, and we welcome adopters from any state. We have access to a transport to Aurora, CO. Other out of state adopters either travel to Missouri or arrange & pay for air transport. Virtual meet and greets are available on the appointment request. ##2755256##
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Photo of Reef

Reef

Mastiff Great Pyrenees

Male, 1 mo
Aurora, CO
Size
(when grown) Large 61-100 lbs (28-45 kg)
Details
Good with kids, Good with dogs, Good with cats, Spayed or Neutered, Shots are up-to-date,
Story
Meet this splashingly adorable puddle of puppies! Introducing Cove, Sea, Brook, Ocean, Reef, Harbor, Bayou, Lake & Creek! They are ready to send waves of love, fun, and playfulness right into your homes. Born to their mama Freya, these pups are going to make excellent dogs. They are a great mix of Great Pyrenees, Mastiff and who knows what- so they are sure to be big pups. NOTE: They will be available to meet at the PetSmart Adoption Event in Springfield, MO on Saturday, June 20. Come meet them and take one home! If you're interested in adopting me, please fill out an application at www.polkcountyhumanesociety.org/adopt. You can also reserve an appointment to meet me. Some pets are in foster homes or may already have visits scheduled, so appointments help ensure I’ll be available. Polk County Humane Society is located in Bolivar, Missouri, and we welcome adopters from any state. We have access to a transport to Aurora, CO. Other out of state adopters either travel to Missouri or arrange & pay for air transport. Virtual meet and greets are available on the appointment request. ##2755257##

These pups are in Boulder, Colorado too!

Below are our newest added Mastiffs available for adoption in Boulder, Colorado. To see more adoptable Mastiffs in Boulder, Colorado, use the search tool below to enter specific criteria!
Photo of Sporty Spots

Sporty Spots

American Bulldog St. Bernard

Male, Adult
Boulder, CO
Size
(when grown) Large 61-100 lbs (28-45 kg)
Details
Good with kids, Good with dogs, Not good with cats, House-trained, Spayed or Neutered, Shots are up-to-date,
Story
Sporty Spots is a very handsome Saint Bernard American Bulldog mix that weighs about 80 pounds! He absolutely loves people and loves to get attention and belly rubs! He will sit with his head in your lap getting all the head scratches for hours if you let him. He is a goofball and is sure to make you laugh and smile everyday.  Spots is a super friendly and outgoing dog. He is good with children that are aged 14 and over! He loves toys, and he also loves to play in water. He is the kind of dog that would love to play in the sprinklers and have his own little pool he can play in. He really loves to play with balls, he will chase them all day. Spots would do best in a home that has a backyard for him to run around in.  Spots does well with some dogs that are his size or larger. Spots will need to go to a home that has a strong handler and has owned large dogs before. So far, he has learned to sit, stay, and lay down.  Overall, Spots is an amazing dog that is waiting for his forever home. He is very loyal and very friendly with other people. He also is very protective of his home and loves to keep patrol of his yard! He loves toys and water and would make the perfect travel buddy! If interested in Zee Bo please go to https://www.ozzieandfriendsrescue.org/adoptions Ozzie and Friends Rescue makes arrangements for all dogs adopted to be transported all across the West Coast .  June 18, 2026, 12:28 pm
Photo of Bo Maverick

Bo Maverick

Belgian Malinois Neapolitan Mastiff

Male, Adult
Boulder, CO
Size
(when grown) Large 61-100 lbs (28-45 kg)
Details
Good with kids, Good with dogs, Spayed or Neutered, Shots are up-to-date,
Story
Meet Bo Breed: Belgian Malinois / Mastiff Mix Sex: Male DOB: August 3, 2022 Weight: 70 Pounds Health: Healthy and doing well Bo is a handsome, intelligent boy with a big heart and an even bigger personality. This energetic Malinois/Mastiff mix combines the loyalty and devotion of both breeds with a playful spirit that makes every day feel like an adventure. Sadly, Bo has become one of the rescue’s long-timers, patiently watching other dogs leave for their forever homes while he continues to wait for someone to notice him. He deserves the chance to finally leave the shelter behind and start the life he’s been hoping for. Personality Bo is affectionate, loyal, and full of joyful energy. He loves interacting with people and thrives on connection and companionship. His playful personality keeps life fun, whether he’s enjoying a walk, learning something new, or simply spending time close to his humans. Bo forms strong bonds and becomes deeply devoted to the people he trusts. His sweet nature and loving heart make him a wonderful companion who truly wants to be part of a family. Breed Info A Belgian Malinois and Mastiff mix combines intelligence, strength, and loyalty. Malinois are known for their sharp minds, trainability, and desire to work closely with their owners, while Mastiffs bring calm confidence and deep devotion to their families. Dogs with this mix tend to be incredibly loyal and thrive when given both mental stimulation and physical activity. With structure and engagement, they become deeply bonded companions who love being involved in daily life. Owner Responsibilities Bo already has a foundation of basic training, but like many intelligent dogs, he will benefit from continued training and mental enrichment. Regular exercise such as daily walks, play sessions, and activities that challenge his mind will help keep him happy and balanced. Positive reinforcement training will strengthen the bond between Bo and his adopter while helping him continue to grow into a confident, well-mannered companion. ⚠️ Things to Consider Before adopting Bo, it’s important to think about your long-term lifestyle and stability. Are pets allowed where you live now and in the future? If you move, will Bo move with you? Do you have the time each day to provide exercise, engagement, and companionship? Are you financially prepared for routine veterinary care, food, and unexpected medical needs? Dogs like Bo deserve a home that is committed to them for life. Vet Care Even though Bo is healthy, adopters should establish care with their own veterinarian soon after adoption. This helps ensure preventative care continues properly and provides a trusted medical partner for Bo’s long-term health and well-being. Understanding the 3-3-3 Rule Like most rescue dogs, Bo will need time to adjust to his new home. The first 3 days he may feel unsure as he decompresses from the transition. The first 3 weeks he will begin learning your routine and feeling more secure. By 3 months, his confidence will grow and his full personality will shine. Patience and consistency during this adjustment period will help Bo thrive. Why Bo? Bo has waited patiently for someone to see the amazing dog he truly is. He is loyal, playful, intelligent, and full of love to give. Long-timer dogs like Bo often become the most devoted companions because they know what it means to finally be chosen. The family who gives Bo his forever home will gain a faithful friend who will stand by their side through every adventure. Adoption Information If you are interested in adopting this wonderful dog, please complete an adoption application by visiting: https://www.ozzieandfriendsrescue.org/adoptions Thank you for considering adoption through Ozzie and Friends Rescue, a Los Angeles–based rescue dedicated to giving dogs a second chance at a loving home. Our team carefully reviews every application and will reach out to help match you with the right dog for your home and lifestyle. You may be seeing our dogs listed in your state because we work hard to give as many of our rescue dogs as possible the opportunity to be seen by loving families beyond our local area. While we are based in Los Angeles, we expand our reach throughout the Western United States and the Midwest to help more dogs find the forever homes they deserve. We understand that transportation and adoption fees can sometimes feel like a big commitment, and we truly appreciate every person who considers opening their heart and home to a rescue dog. Our goal is simply to give these dogs the best chance at being seen, adopted, and loved. Ozzie and Friends Rescue coordinates safe and reliable transport so adopted dogs can travel to their new homes across the Western United States, Canada, and the Midwest. We can’t wait to help you meet your next fur-ever best friend. June 18, 2026, 12:28 pm

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Mastiff shelters & rescues in Boulder, Colorado

There are animal shelters and rescues that focus specifically on finding great homes for Mastiff puppies in Boulder, Colorado. Browse these Mastiff rescues and shelters below.

Here are a few organizations closest to you:

Shelter

2.1 miles

Humane Society of Boulder Valley

2323 55th Street, Boulder, CO 80301

Pet Types: cats, dogs, small animals

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Rescue

23.1 miles

Ace of Hearts Dog Rescue - CO Transport Stop

711 Walnut St, Boulder, CO 80203

Pet Types: dogs

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Rescue

25.3 miles

Ho-Bo Care Boxer Rescue

Denver, CO 80209

Pet Types: dogs

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Shelter

29.2 miles

Polk County Humane Society (in Missouri) - Colorado Transport

3511 N Salida Court, Aurora, CO 80011

Pet Types: cats, dogs

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Shelter

30.6 miles

Humane Society of the South Platte Valley

2129 W Chenango Ave, Littleton, CO 80120

Pet Types: cats, birds, dogs, rabbits, small animals

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Rescue

34.6 miles

Big Dogs Huge Paws, Inc

PO Box 460699, Aurora, CO 80046

Pet Types: dogs

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Rescue

35.9 miles

Big Bones Canine Rescue

Windsor, CO 80550

Pet Types: dogs

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Rescue

36 miles

Homeward Bound Rescue of Colorado

Greeley, CO 80634

Pet Types: dogs

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Rescue

37 miles

All Aboard Animal Rescue

Fort Collins, CO 80526

Pet Types: cats, dogs

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Looking for a specific shelter or rescue?

If you're not seeing what you're looking for, try our shelter and rescue search. We have more than 17,000 organizations in our database with furry pals waiting for a new home!

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Want to learn more about adopting a Mastiff puppy or dog?

We've got all the info you need on adopting and caring for a Mastiff puppy. Check out the links below for everything you ever wanted to know about Mastiff puppies and adults.

Mastiff basics

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Where do Mastiffs come from? How many types of Mastiffs are there? From the history of the breed to question about average height, weight and size, brush up on these basic facts about the Mastiff.

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