Bush said on Twitter Monday that Sully is a beautiful and beautifully trained golden lab from the America's VetDogs non-profit organization in New York.
The group provides service dogs to veterans in need.
The former president said he could not be more grateful, especially for the organization's commitment to veterans.
If you'd like to follow Sully's adventures, he has his very own Instagram account: @SullyHWBush.
WATCH: Presidents and their pets
Happy National Pet Day! Here's presidents and their pets