Pet Keen is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.

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

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

cardigan welsh corgi puppy

Vet approved

Dr. Maxbetter Vizelberg  Photo

Reviewed & Fact-Checked By

Dr. Maxbetter Vizelberg

Veterinarian, DVM

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

Learn more »

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 six and nine 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 six to nine months, a small breed male dog can be fertile and sire pups as young as five 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 nine to eleven 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 its 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 seven to ten days, but the fertile time for a female dog can last up to three 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 Credit: 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 five 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 Credit: 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 prior to 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 Credit: 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.

Featured Image Credit: Liliya Kulianionak, Shutterstock

Our vets

Want to talk to a vet online?

Whether you have concerns about your dog, cat, or other pet, trained vets have the answers!

Our vets