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How to Tell if a Puppy Is a Boy or a Girl: Vet-Approved Way

Written by: Elizabeth Gray

Last Updated on February 15, 2024 by Dogster Team

African female veterinarian examining Yorkshire Terrier puppy

How to Tell if a Puppy Is a Boy or a Girl: Vet-Approved Way


Dr. Amanda Charles Photo


Dr. Amanda Charles

BVSc MRCVS (Veterinarian)

The information is current and up-to-date in accordance with the latest veterinarian research.

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While you can’t always tell the difference between male and female adult dogs from a distance, there are physical and behavioral clues that can help. When it comes to puppies, however, especially newborns, it can be a lot harder to tell if a puppy is a boy or a girl.

If you’re dealing with a litter of newborn puppies or just aren’t sure how to determine the sex of your new baby dog, we’re here to help. In this article, we’ll teach you how to tell if your puppy is a boy or a girl and discuss the differences between the two.

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Before You Begin

Be cautious about removing newborn puppies from their mother. Some mother dogs are very protective and it’s important to give them time and space to bond with their puppies. While you should keep handling to a minimum for the first few weeks of their lives, you will need to touch the puppies occasionally.

For example, you’ll want to monitor their weight to make sure they’re growing properly and to see if they are boys or girls. Consider having someone else take the mama dog for a short walk in the yard while you check on the puppies if she is especially protective.

Playing puppies
Image Credit: Anita Kot, Getty images

How to Tell if a Puppy Is a Boy or a Girl

1. Don’t Rely on Size

For most breeds, adult male dogs are taller and heavier than females as a breed standard. However, you can’t rely on the size of newborn puppies to tell the boys from the girls.

The birth weight, overall health, and other factors play a role in the puppy’s size. You can’t always assume the bigger babies are the boys.

2. Don’t Rely on Behavior

We’ll discuss some of the behavior differences between male and female adult dogs later in this article. Many of those behaviors are related to hormones and other changes that occur once the dog reaches sexual maturity.

Newborn puppies haven’t undergone these changes yet, so you can’t rely on their behavior to tell you which are boys or girls.

3. Physically Examine the Puppy

To tell if a puppy is a boy or a girl, pick the dog up and look at the belly. At this age, the penis and vulva are similar in size and appearance but are in different locations.

Girl puppies have a visible vulva, often described as leaf-shaped, between their hind legs below the tail. Boy puppies have a penis further up their belly, just below their umbilical area or belly button. These physical features are apparent even in puppies who were just born.

Close up of a sleeping dog penis
Image Credit: Cheevarut, Shutterstock

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Why Is It Important to Know if a Puppy Is a Boy or a Girl?

If you’re selling or adopting out puppies, you’ll need to be able to tell new owners the sex of the dogs. Most owners prefer male or female dogs based on past experience, the sex of dogs currently in their family, advice from other dog owners, or general assumptions about the behaviors of the two sexes.

According to research, there are differences between male and female dogs, but the data shows some variability. For example, male dogs are more likely to be aggressive and courageous than females. Females show more fearful behaviors on average but are more inclined towards social interactions with humans that require cooperative skills. Males were more inclined towards social play with people.

However, whether your puppy is a boy or a girl isn’t the only factor that controls how they act. Early socialization and training play a vital role in shaping a puppy’s temperament and behavior as they develop.

Two little german shepherd puppies sitting on the lawn
Image Credit: Rita_Kochmarjova, Shuttertstock

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Determining if a puppy is a boy or a girl at any age is easy once you know what you’re looking for. Deciding whether a boy or girl dog is the best fit for your family might be a bit harder. As we mentioned, it often comes down to the owner’s personal preference. If you don’t plan to breed your boy or girl puppy, talk to your veterinarian about the best time to have them spayed or neutered.

Featured Image Credit: Jose Luis Pelaez Inc, Getty Images

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