Ideally, it is a good decision to buy a Shih Tzu when it is around 8 to 10 weeks old. Getting the pet before or after that age can cause issues in catering to them. Especially if you are a first-time pet parent, getting a Shih Tzu that is younger than 8 weeks would require you to put in a lot of time and effort in tending to it all day long. You need to be extra careful at this age and cannot afford to be careless. On the other hand, getting a Shih Tzu older than 10 weeks becomes difficult to train. As most essential habits are already formed at this age, you may find it difficult to teach new commands and tricks to your pet.