Not only is he a little boy's best friend, he is also his lifesaver.
On three occasions, Costa the dog has prevented autistic Henry Smyth (11) from running into traffic while attempting to cross the road.
Henry's mother, Barbara, said the 18-month-old black Labrador, who has been looking after her son since September, had also helped Henry socialise better at school and at home in Castlerock, Co Londonderry.
Whether it is anchoring himself on the spot to stop Henry running off, or licking the boy's cheeks and ears when he is upset, the family called Costa a "Godsend".
"When we are outside, Henry wears a back pack that is attached to Costa, who is led by me or my husband," Mrs Smyth told the Belfast Telegraph.
"With his learning difficulties, Henry cannot comprehend the dangers of traffic, and has a tendency to dash out. But Costa just sits down and anchors Henry from moving and keeps him safe. He's like an extra pair of hands and ears when keeping Henry safe."
Costa - named after the coffee house chain that sponsored him - was given to Henry by the charity Assistance Dogs NI. He spent months in training with experts in Belfast before he went to live permanently with the little boy and his family.
There is now an amazing bond between Henry, who was diagnosed with autism aged three, and his lifesaver pet.
At night, Costa even lies at Henry's bedside and waits until he is asleep before he goes to his own bed.
The bond also means that Barbara can now enjoy a simple trip to the supermarket with her three children, which she was able to do for the first time on Wednesday.
"I know that for many families with children, going to the supermarket can be a bit fraught, but with a child with autism, it can really be hard," she said.
"Henry can find things too stressful and would often have a complete meltdown and would lie and scream on the floor. For us to all to go out together as a family without incident was absolutely amazing.
"When Henry began to feel a bit unsteady, I would just say for him to sit down and then Costa would lick his face and Henry would calm down.
"The public response that Henry and Costa have been getting is really positive.
"People come over and ask about the dog, and now Henry is talking to them - something he would never do before. [He has started] to point out Costa's nose, ears and legs to them. Costa is an absolute Godsend and he's a real hero to our family."
While the Labrador is dearly loved by Henry, his parents, Barbara and Warren, and eight-year-old twins Emily and Christopher, he is not a standard pet dog and his training and discipline has to be maintained.
But even being mindful of Costa's routine has helped Henry in his everyday life.
Mrs Smyth explained: "Costa's food has to be weighed out each day and although Henry hates routine, helping to do this small job for Costa is also helping him with learning about routine.
"Costa is even encouraging Henry to learn how to put on his clothes. He's just brilliant.
"We cannot thank Assistance Dogs NI for Costa and for changing Henry's life and ours as a family."