At what age is a Corgi fully grown?

A Corgi reaches adulthood at 18 months. As a small breed it has a relatively long lifespan and develops more slowly when young. Generally, Corgis become sexually mature at 6–8 months with their first heat, marking the start of adolescence.

By 12 months, roughly equivalent to a 15-year-old human, their temperament becomes more stable, their size changes little, and their coat thickens. It is only at 18 months that the body is fully set and the Corgi is considered an adult.