Yorkshire Terriers can typically get their first full haircut and styling around nine months old, although a light trim can be done at three months to tidy them up.

It's generally recommended to wait until a puppy is about nine months old before getting a full groom and style. Dogs go through what is often called an "awkward" or "puppy uglies" phase around six months, which is when they shed a lot of their puppy coat and grow their adult coat. Grooming is usually not recommended during this time due to the excessive shedding which can impact the final look of the style.
Grooming Frequency: How Often Should Your Dog Get a Haircut?
Generally speaking, you can take your Yorkshire Terrier to the groomer for a styling session every three months. However, this may be adjusted depending on the season. In the summer, you might opt for more frequent grooming, while in the winter, you may choose longer intervals between appointments. Additionally, some dogs’ hair grows faster than others, which may necessitate more frequent grooming. On average, most Yorkies need professional styling three to four times a year. Regular at-home maintenance such as brushing is also crucial to prevent matting. It’s also common to get a trim approximately every two months for most dogs. However, some owners allow their dog’s coat to grow out a bit as it can be very attractive, and that reduces the need for frequent trimming.