Noticing that your dog only has one testicle can be surprising and concerning for many owners.
While it may not seem like an immediate health problem, this condition can have important implications for your dog’s long-term health and comfort.
We outline the common reasons why a dog may only have one testicle, what you can do, and when to seek veterinary help.
Dog Only Has One Testicle — Why It Happens
A dog only having one testicle is usually the result of a condition called cryptorchidism, where one or both testicles fail to descend into the scrotum. This can be congenital (present at birth) and is often linked to genetics, but in some cases, the retained testicle can be located in the abdomen or inguinal canal where it is not visible or easy to feel. In rare situations, trauma, surgical history, or hormonal influences may also play a role.
While some dogs may not show outward signs of discomfort, a retained testicle carries serious health risks such as infertility, torsion, and an increased likelihood of testicular cancer.
Dog Only Has One Testicle: Common Causes
Cryptorchidism (Retained Testicle)
The most common reason a dog only has one testicle is cryptorchidism. Normally, both testicles descend into the scrotum by 8 weeks of age, but in dogs with cryptorchidism, one (or sometimes both) fail to move into place.
This retained testicle may be stuck in the groin area or remain inside the abdomen.
Owners may notice that their dog’s scrotum only appears to hold one testicle, even as the dog matures. This condition is not just cosmetic — retained testicles can become twisted, painful, or cancerous over time, making veterinary evaluation essential.
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Genetic Factors
Genetics play a major role in why some dogs develop cryptorchidism. Breeds such as Chihuahuas, Pomeranians, Boxers, and Yorkshire Terriers are more likely to experience this condition.
Because it is inherited, dogs with cryptorchidism should not be bred, as they may pass the trait down to their offspring.
For owners, this often means learning that their dog’s condition was not preventable but rather a genetic predisposition. Responsible breeding practices can help reduce the risk in future generations.
Abdominal or Inguinal Retention
In some cases, the missing testicle is not gone — it is just located where it cannot be easily seen.
Retained testicles can hide in the inguinal canal (the passageway between the abdomen and scrotum) or remain fully inside the abdomen.
Dogs with abdominal testicles may show no symptoms initially, but these retained testicles can be at higher risk for complications like testicular torsion or tumors. An ultrasound or other imaging may be needed to determine the exact location of the missing testicle.
Hormonal or Developmental Issues
Occasionally, hormonal imbalances or developmental problems during puppyhood may interfere with normal testicular descent.
These are less common but can still lead to a situation where one testicle fails to appear in the scrotum.
In these cases, owners may also notice other growth or maturity concerns, which makes early veterinary involvement especially important.
Trauma or Surgical Removal
Although less common, trauma can sometimes result in the loss or damage of a testicle. Similarly, if a dog has had surgery such as castration of one testicle due to injury or disease, the scrotum may only contain one.
Owners may be aware of the dog’s medical history in these cases, but if not, a missing testicle may warrant asking whether the dog had a prior surgical procedure.
What to Do If Your Dog Only Has One Testicle
If you notice your dog only has one testicle, the first step is to schedule a veterinary examination. Your vet will check whether the missing testicle is retained in the abdomen or groin and may recommend imaging if needed.
At home, you can monitor your dog for changes such as swelling, discomfort, or changes in urination, which may signal complications.
Neutering is strongly recommended for dogs with cryptorchidism, as leaving a retained testicle in place dramatically increases the risk of cancer. Even if your dog seems healthy, this preventative surgery can save them from serious issues later on.
Avoid breeding a dog with only one testicle, since the condition is often genetic. Instead, focus on giving your pet a happy, healthy life with regular veterinary care, a balanced diet, and plenty of exercise.
It can also be helpful to track your dog’s growth milestones. If you have a puppy and only one testicle has descended by the age of 6 months, it is unlikely the other will appear. Early intervention can help plan the safest treatment path forward.
When to Call or Visit Your Vet
You should always consult your vet if your dog only has one testicle, regardless of age. While some owners may not see immediate symptoms, the health risks of cryptorchidism make professional evaluation essential.
Seek urgent veterinary care if your dog shows signs of pain, swelling in the groin or abdomen, or sudden distress, as these may indicate testicular torsion — a painful and potentially life-threatening condition.
Another reason to visit the vet promptly is if your dog is approaching sexual maturity without both testicles present. Retained testicles can become cancerous over time, and proactive neutering can prevent this risk.
Even if your dog is older, it is never too late to address the issue. A veterinary checkup can help ensure your pet remains healthy and prevent future complications.
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Key Takeaway
A dog only having one testicle is most often due to cryptorchidism, a condition where one testicle does not descend properly.
While it may not cause immediate discomfort, it carries significant long-term risks such as infertility, torsion, and cancer.
The best step you can take is to have your dog evaluated by a veterinarian and follow their guidance, which usually involves neutering to protect your pet’s health.
With prompt care and responsible management, dogs with this condition can go on to live happy, healthy lives.