When do Great Pyrenees stop growing?

Great Pyrenees are a large and slow-maturing breed. Most Great Pyrenees reach their full adult size by the time they are around two years old, although they might continue to fill out and develop muscle mass beyond that age. Great Pyrenees puppies experience their most rapid growth during their first year of life, but their growth plates don’t close until they are around 18 to 24 months old.