It depends. Larger breeds, it's between 4-6 weeks, usually about 6. Because Chihuahua puppies are so delicate and more susceptible to disease and other bad stuff, most breeders won't release them to new owners until 6-8 weeks of age or longer. I took Cooper at 7 1/2 weeks, I think... maybe 6 1/2. Most times, the chi breeder will decide on an individual basis when to release them to new owners.