Instructions
Gently lift the puppy and hold him belly up. The puppy will be squirmy and wiggly which will make a closer look a bit more difficult. Stroke the puppy gently on his chest so you can calm him down.
Find the umbilical cord, or belly button. If you know where the belly button is, there is less of a chance you will mistake it for a penis.
Look just under the belly button, if the puppy is a male, you will see a small, rounded penis. Young puppies cannot expose their penises, so do not attempt to make the penis come out of the body. It cannot.
Look carefully between the puppy's legs. If the puppy is a female, you will see a leaf-shaped vulva with a vertical slit, which is the vagina.
Compare litter mates if you still have trouble determining the gender of a puppy, the two sexes should be obvious in their differences.
How to Determine the Gender of a Puppy
Sexing a puppy gets easier the older the puppy gets. It is much harder to determine the gender of a newborn puppy than it is a puppy who is eight weeks of age. It is easy to mistake the umbilical cord stump, or belly button, for a penis. But with practice, you will be able to tell the boys from the girls.