Stages of Growth: 12-Week-Old Puppy Behavior and Development

Updated on April 4, 2017
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Adrienne is a former veterinary hospital assistant, certified dog trainer, behavior consultant, and author of "Brain Training for Dogs."


What Are 12-Week-Old Puppies Like?

If you're planning on getting a 12-week-old puppy or have one already, then you're probably wondering if his behavior and development are within the norm for his age range.

12 weeks is usually the normal age for dogs to be sent home from the breeder. This mostly applies to smaller breeds. For example, Maltese puppies don't usually go to their new homes until they are 12-weeks-old because they are still not fully developed, both mentally and physically.

Larger breeds, such as Labs, are usually ready to go to their new homes at 8 weeks. If you purchase from a breeder, any puppy older than 8 weeks may have been a singleton (the only puppy of the litter) or it was left over from a litter that has already been sold. Owners also sometimes return puppies to the breeder if they were not a good match. Of course, puppies may likely be older than 12 weeks if you go to a shelter.

Regardless, this article will cover almost everything there is to know when dealing with your new buddy. Normally, at this age, puppies are a handful, but luckily, puppyhood goes by really fast. You might even find yourself missing your pet's funny quirks.

This 12-week-old puppy has lost her lower incisors.
This 12-week-old puppy has lost her lower incisors. | Source

12-Week-Old Puppy Development

At this age, they are only a fraction of what they'll be as adults. They have all the cute neotenic traits of younger puppies, but they are also a tad bit taller and longer, and their muzzles are starting to gradually lengthen.

Soft Hair

At this age, the puppies are still covered in soft hair that, fortunately, sheds very little. They will need a very delicate shampoo that is pH balanced. This is a good age to introduce the puppy to bathing. Be sure to make the experience positive and fun. You can also use dog wipes that are hypoallergenic and alcohol-free for cleaning in between baths.


Your puppy should have 28 baby teeth. It's still too early for them to get their adult teeth, which should come in within the next three months. Their teeth start falling out between the ages of 12 weeks to 7 months. They'll first lose their incisors, then the premolars, and finally the canines. You may find the occasional baby tooth in their water bowl. At 3-4 months of age, it's a good idea to have the vet check your dog's mouth to make sure there are no bite problems and that the teeth are growing normally.

At this stage of development, your pup will start chewing, and it's your job to find safe chew toys and treats that are suitable for his age. Puppy teeth are delicate, and an adult dog bone or toy may fracture them. Also keep in mind that their digestive system has not fully developed, so they will need easy-to-digest foods. I recommend Nyablone's Healthy Edibles and Nutri Dent Chews with the label "3-month-old puppy" somewhere on the packaging.

To help relieve sore gums, freeze a clean rag that's been soaked in water and wrung out. Chewing on this will soothe your puppy's gums. You should also get your dog acquainted to having his teeth brushed.

Better Bladder Control

This is a good time to start crate training. Generally speaking, you can expect a 3-month-old puppy to be able to hold urine for 2 to 4 hours, depending on how much he drank and his activity levels. Some puppies at this age can also hold it through the night.


The first vaccine is usually given at 6-8 weeks at the breeder, but your puppy will need another one at 12 weeks. This second vaccination will likely contain distemper, adenovirus, hepatitis, parainfluenza, parvovirus, and lepto. Lepto is generally given when a pup is 12 weeks or older and never before. The rabies vaccine is also given after 12 weeks.


Failure to provide your pet with a chewing toy will result in a rambunctious dog that will chew up furniture, shoes, and even the wall.

12-Week-Old Puppy Behavior

If you are planning on adopting a puppy, make sure you puppy proof your home to keep the furball safe and out of trouble. If you have ever had kids, think of this as the "toddler stage" when everything had to be safely stored away. But, unlike a toddler, your 12-week-old puppy will not be wearing diapers and will have sharp teeth. Following are some common behaviors of a dog that is 3-months-old.

Boundless Energy

Your puppy will romp around and play all day. His gait is still quite clumsy, but he'll gradually be better coordinated. If you see your dog running really fast in circles, it is normal. They are just excited and having fun. Dog owners often call these the "zoomies." The good thing is that all of this activity will tire them out quickly and they will have no problem sleeping. Expect puppies of this age to sleep soundly for about 18 to 20 hours a day. The rest of the day is then spent playing, eating, and eliminating.

Curious and Adventurous

At this age, puppies are learning all they can about the world around them. In the wild, mother wolves, encourage 10 to 12-week-old puppies to use the den less and instead explore the great outdoors in special rendezvous areas, quite similar to open-air kindergartens. Domestic puppies also love to explore their surroundings, and often mouth objects just as babies do. This is why you should puppy proof your entire home!


Mine, mine, mine! Just as a toddler is not willing to share his toys with other toddlers, 12-week-old puppies go through a possessive stage in which they may have a desire to guard their food and toys against other dogs and people. In the wild, once out of the den, this instinct helped young pups from starving. However, in a domestic setting, you may want to nip this behavior in the bud by tackling resource guarding before it gets out of hand.

Separation Anxiety

Young puppies may throw a fit when they are left alone. It's important to gradually train your buddy to be alone. Try to avoid rushing to your pup when she is whining and crying. Rather, wait for her to calm down before you return to her. Doing so will teach her that calm behavior gets you back. Of course, before trying this method, make sure all your pup's needs are met. She may be whining because she's thirsty or needs to go outside to potty.


At 12 weeks, your dog is in the full puppy socialization phase. This is the best age to take her to classes. Do your best to get her to meet different people, pets, and children. Organize puppy parties so your puppy has the opportunity to meet as many different people as possible. For safe socialization tips, visit the Operation Socialization website.

As you can tell, 12-week-old puppies go through a whole lot of growth and change! Enjoy this phase as puppyhood is very short.

© 2013 Adrienne Janet Farricelli


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    • profile image

      Lynn 7 months ago

      Enjoyed reading about young pups.

      I have a 4 month old Labrador her energy level is virtually limitless the only problem I get is her teeth sink into my hands and arms no amount of saying no biting helps hopefully she will grow out of it.

      Thanks again for your much appreciated knowledge.

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      Donna 7 months ago

      Very interesting

    • alexadry profile image

      Adrienne Janet Farricelli 4 years ago from USA

      And the puppy stage is just so short! Puppies are the cutest things!

    • Jennifer Bart profile image

      Jennifer Bart 4 years ago from Texas

      Great hub! Very informative and well organized. Reading this makes me miss my dogs puppy stage! I really enjoyed reading this.