Meet the dog who smiles on command

Fans of Herbert's grin watched the video over and over again. Photo / Facebook

He may be waiting for a home but it seems nothing can keep the smile off this dog's face.

A video of "Herbert", a dog awaiting adoption, has gone viral after being posted to Facebook by a pet foster carer in Chicago.

The post has been shared almost 300, 000 times in three days and attracted comments from viewers seemingly overwhelmed by the dog's cuteness.

Fans of Herbert's grin watched the video over and over again. Photo / Facebook

Foster carer Robles later shared a second post telling viewers "now that he made you laugh, help find him a home".

- nzherald.co.nz