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At What Age Do Dogs Reach Sexual Maturity? What Science Says!

Written by: Nicole Cosgrove

Last Updated on July 12, 2024 by Dogster Team

cardigan welsh corgi puppy

At What Age Do Dogs Reach Sexual Maturity? What Science Says!


Dr. Maxbetter Vizelberg  Photo


Dr. Maxbetter Vizelberg

DVM (Veterinarian)

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

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Like children, puppies grow and mature way too quickly. One minute you are delighting in the “puppiness” of your new addition, then before you know it, your adorable pup is on the sofa humping away at the pillow.

Unfortunately, they do not stay puppies for long, and most dogs become sexually mature between 6 and 9 months old. It can vary, however, according to the size and breed of the dog.


When Do Puppies Reach Sexual Maturity?

The age of sexual maturity for your pup will depend on the size and breed of your dog. While the average age is between 6 to 9 months, a small breed male dog can be fertile and sire pups as young as 5 months old. However, most dogs become fully fertile at around 12 to 15 months old, and giant breeds may not be sexually mature until they reach 12 to 18 months of age.

Since spaying and neutering your dog can alter hormones that aid in healthy bone growth, many veterinarians do not recommend having the procedure done until the canine’s growth plates close. This usually occurs by the time a dog reaches 9 to 11 months of age.

shiba inu puppy dog with collar tracker lying on the beach
Image Credit: Julija Kumpinovica, Shutterstock

What Happens as Your Puppy Reaches Sexual Maturity?

As your pup begins to hit sexual maturity, hormonal changes may affect their behavior and personality. These changes will differ between males and females.

Female Dogs

Signs that your sexually mature female is in heat include a swollen vulva, frequent urination, and licking of the genital area. The dog will have a red vaginal discharge which resembles a woman’s period for 7 to 10 days, but the fertile time for a female dog can last up to 3 weeks.

The first female heat can begin between 6 and 15 months of age, depending on the individual breed. Although a female can get pregnant during her first heat, it is not recommended. During this time, it is important to watch her closely and keep her on a leash when outside until she gets spayed. Otherwise, you can end up with an unwanted pregnancy.

female goldendoodle puppy
Image By: cine-nomadic, Shutterstock

Male Dogs

Male dogs are most fertile after they reach 12 to 15 months of age. They can make puppies as young as 5 months old, however. Males are full of testosterone and sexually active all year round at this stage of sexual maturity. As a result, other dogs may begin to show signs of aggression if they sense elevated levels of testosterone, and this can also be a frustrating time for pet parents since males may start to urine-mark their surroundings, even in the home.

At this stage of sexual maturity, both male and female dogs are known to begin to wander away from the house in search of a mate and should be closely monitored, leashed, or contained.

Great Dane puppy with floppy ears walking
Image By: Dmussman, Shutterstock


Neutering and Spaying

Once your dog reaches sexual maturity, you will need to decide when to have the dog spayed or neutered. Most veterinarians will recommend having the procedure done unless you plan to show or breed the dog. However, some vets will recommend having a male neutered before sexual maturity, and others will advise you to wait until he is 7 to 15 months of age.

When to have your female pup spayed will depend on the individual dog. It is important to wait until she is finished growing and has completed one heat cycle. Otherwise, you run the risk of orthopedic problems in the future.

According to the American Kennel Club (AKC), “Research results have shown that early spay or neuter (before the age of 12 months) can impact the incidence of different types of cancer, hip dysplasia, and development of canine cruciate ligament ruptures.”

Since having your pet spayed or neutered is an individual decision, you should discuss any concerns with your veterinarian. Then, you and your vet can make the best decision that is best for your dog.

dog ongoing spaying surgery
Image By: ARVD73, Shutterstock



Sexual maturity in dogs is inevitable. It is important to identify the behaviors associated with sexual maturity so you can avoid unwanted pregnancies. Whether you have a female dog in heat or a male that is humping and marking everything in sight, you will need to decide if you are going to have the dog fixed. It is recommended that you discuss any growth concerns with your veterinarian prior to scheduling the procedure so you can prevent orthopedic problems in the future.

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Featured Image Credit: Liliya Kulianionak, Shutterstock

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