My 8-week-old puppy hasn't pooped since coming home. Should I worry?

Hello, and thanks for using Petco Pet Education Center, formerly Petcoach! I would not be concerned at this time. Sometimes a sudden change in environment can cause bowel movement irregularities. If Mia still has not had a BM by tomorrow, make sure to mention it to the vet. If she does, it is a good idea to collect in in a plastic bag so that they can use it to check for intestinal parasites, which are common in puppies. I usually recommend that you continue to feed the food she was on from the breeder to avoid digestive upset. Make sure she has access to clean, fresh water, which will help keep stools moist and easy to pass.