The American Mastiff is a large and serious looking dog, but they are actually quite docile and affectionate with their families. These non-aggressive dogs get along well with children and other pets in the home, but they won’t hesitate to defend the family if they sense a threat. They form strong bonds with their owners and love to spend time playing games and running around outdoors with them. Despite their sober demeanor, these dogs love to clown around when they aren’t content to just laze about. Their kind and loyal nature of these dogs has added greatly to the continued popularity of the breed.